rcutorture: Print time since GP end upon forward-progress failure
If rcutorture's forward-progress tests fail while a grace period is not
in progress, it is useful to print the time since the last grace period
ended as a way to detect failure to launch a new grace period. This
commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
rcutorture: Print histogram of CB invocation at OOM time
One reason why a forward-progress test might fail would be if something
prevented or delayed callback invocation. This commit therefore adds a
callback-invocation histogram printout when OOM is reported to rcutorture.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
rcu: Account for nocb-CPU callback counts in RCU CPU stall warnings
The RCU CPU stall warnings print an estimate of the total number of
RCU callbacks queued in the system, but this estimate leaves out
the callbacks queued for nocbs CPUs. This commit therefore introduces
rcu_get_n_cbs_cpu(), which gives an accurate callback estimate for
both nocbs and normal CPUs, and uses this new function as needed.
This commit also introduces a rcu_get_n_cbs_nocb_cpu() helper function
that returns the number of callbacks for nocbs CPUs or zero otherwise,
and also uses this function in place of direct access to ->nocb_q_count
while in the area (fewer characters, you see).
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
rcutorture: Dump grace-period diagnostics upon forward-progress OOM
This commit adds an OOM notifier during rcutorture forward-progress
testing. If this notifier is invoked, it dumps out some grace-period
state to help debug the forward-progress problem.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
rcutorture: Prepare for asynchronous access to rcu_fwd_startat
Because rcutorture's forward-progress checking will trigger from an
OOM notifier, this notifier will introduce asynchronous concurrent
access to the rcu_fwd_startat variable. This commit therefore prepares
for this by converting updates to WRITE_ONCE().
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Remove return variables (declared as "ret") in cases where,
depending on whether a condition evaluates as true, the result of a
function call can be immediately returned instead of storing the result in
the return variable. When the condition evaluates as false, the constant
initially stored in the return variable at declaration is returned instead.
Signed-off-by: Pierce Griffiths <pierceagriffiths@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 22 Sep 2018 01:08:09 +0000 (18:08 -0700)]
rcutorture: Affinity forward-progress test to avoid housekeeping CPUs
This commit affinities the forward-progress tests to avoid hogging a
housekeeping CPU on the theory that the offloaded callbacks will be
running on those housekeeping CPUs.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Fix NULL-pointer issue located by kbuild test robot. ] Tested-by: Rong Chen <rong.a.chen@intel.com>
Paul E. McKenney [Tue, 28 Aug 2018 21:38:43 +0000 (14:38 -0700)]
rcutorture: Break up too-long rcu_torture_fwd_prog() function
This commit splits rcu_torture_fwd_prog_nr() and rcu_torture_fwd_prog_cr()
functions out of rcu_torture_fwd_prog() in order to reduce indentation
pain and because rcu_torture_fwd_prog() was getting a bit too long.
In addition, this will enable easier conditional execution of the
rcu_torture_fwd_prog_cr() function, which can give false-positive
failures in some NO_HZ_FULL configurations due to overloading the
housekeeping CPUs.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Paul E. McKenney [Mon, 27 Aug 2018 21:43:05 +0000 (14:43 -0700)]
rcutorture: Remove cbflood facility
Now that the forward-progress code does a full-bore continuous callback
flood lasting multiple seconds, there is little point in also posting a
mere 60,000 callbacks every second or so. This commit therefore removes
the old cbflood testing. Over time, it may be desirable to concurrently
do full-bore continuous callback floods on all CPUs simultaneously, but
one dragon at a time.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Paul E. McKenney [Tue, 21 Aug 2018 22:27:16 +0000 (15:27 -0700)]
torture: Bring any extra CPUs online during kernel startup
Currently, the torture scripts rely on the initrd/init script to bring
any extra CPUs online, for example, in the case where the kernel and
qemu have different ideas about how many CPUs are present. This works,
but is an unnecessary dependency on initrd, which needs to vary depending
on the distro. This commit therefore causes torture_onoff() to check
for additional CPUs, attempting to bring any found online. Errors are
ignored, just as they are by the initrd/init script.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit adds a call_rcu() flooding loop to the forward-progress test.
This emulates tight userspace loops that force call_rcu() invocations,
for example, the infamous loop containing close(open()) that instigated
the addition of blimit. If RCU does not make sufficient forward progress
in invoking the resulting flood of callbacks, rcutorture emits a warning.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Merge branches 'bug.2018.11.12a', 'consolidate.2018.12.01a', 'doc.2018.11.12a', 'fixes.2018.11.12a', 'initrd.2018.11.08b', 'sil.2018.11.12a' and 'srcu.2018.11.27a' into HEAD
bug.2018.11.12a: Get rid of BUG_ON() and friends
consolidate.2018.12.01a: Continued RCU flavor-consolidation cleanup
doc.2018.11.12a: Documentation updates
fixes.2018.11.12a: Miscellaneous fixes
initrd.2018.11.08b: Automate creation of rcutorture initrd
sil.2018.11.12a: Remove more spin_unlock_wait() calls
rcutorture/formal: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change,
even though it is but a comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
tools/kernel.h: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change,
even though it is but a comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: <linux-kernel@vger.kernel.org>
net/decnet: Replace rcu_barrier_bh() with rcu_barrier()
Now that all RCU flavors have been consolidated, rcu_barrier_bh()
is but a synonym for rcu_barrier(). This commit therefore replaces
the former with the latter.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: <linux-decnet-user@lists.sourceforge.net> Cc: <netdev@vger.kernel.org>
net/core/skmsg: Replace call_rcu_sched() with call_rcu()
Now that call_rcu()'s callback is not invoked until after all
preempt-disable regions of code have completed (in addition to explicitly
marked RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_sched(). This commit therefore makes that change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: John Fastabend <john.fastabend@gmail.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: "David S. Miller" <davem@davemloft.net> Cc: <netdev@vger.kernel.org>
livepatch: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change,
even though it is but a comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
cgroups: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change,
even though it is but a comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Dennis Zhou <dennis@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Dennis Zhou (Facebook)" <dennisszhou@gmail.com> Acked-by: Tejun Heo <tj@kernel.org>
Now that call_rcu()'s callback is not invoked until after bh-disable and
preempt-disable regions of code have completed (in addition to explicitly
marked RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_bh() and call_rcu_sched(). This commit therefore removes
these two API members from the callback_head structure's header comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Alexey Dobriyan <adobriyan@gmail.com>
percpu-rwsem: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change,
even though it is but a comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Christoph Lameter <cl@linux.com> Acked-by: Tejun Heo <tj@kernel.org>
net/bridge: Replace call_rcu_bh() and rcu_barrier_bh()
Now that call_rcu()'s callback is not invoked until after all bh-disable
regions of code have completed (in addition to explicitly marked
RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_bh(). Similarly, rcu_barrier() can be used in place of
rcu_barrier_bh(). This commit therefore makes these changes.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Roopa Prabhu <roopa@cumulusnetworks.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: <bridge@lists.linux-foundation.org> Cc: <netdev@vger.kernel.org> Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
net/core: Replace call_rcu_bh() and synchronize_rcu_bh()
Now that call_rcu()'s callback is not invoked until after all bh-disable
regions of code have completed (in addition to explicitly marked
RCU read-side critical sections), call_rcu() can be used in place of
call_rcu_bh(). Similarly, synchronize_rcu() can be used in place of
synchronize_rcu_bh(). This commit therefore makes these changes.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: <netdev@vger.kernel.org>
net/sched: Replace call_rcu_bh() and rcu_barrier_bh()
Now that call_rcu()'s callback is not invoked until after bh-disable
regions of code have completed (in addition to explicitly marked
RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_bh(). Similarly, rcu_barrier() can be used in place o
frcu_barrier_bh(). This commit therefore makes these changes.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Jiri Pirko <jiri@resnulli.us> Cc: "David S. Miller" <davem@davemloft.net> Cc: <netdev@vger.kernel.org>
Paul E. McKenney [Sun, 28 Oct 2018 17:32:51 +0000 (10:32 -0700)]
srcu: Use "ssp" instead of "sp" for srcu_struct pointer
In RCU, the distinction between "rsp", "rnp", and "rdp" has served well
for a great many years, but in SRCU, "sp" vs. "sdp" has proven confusing.
This commit therefore renames SRCU's "sp" pointers to "ssp", so that there
is "ssp" for srcu_struct pointer, "snp" for srcu_node pointer, and "sdp"
for srcu_data pointer.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Dennis Krein [Fri, 26 Oct 2018 14:38:24 +0000 (07:38 -0700)]
srcu: Lock srcu_data structure in srcu_gp_start()
The srcu_gp_start() function is called with the srcu_struct structure's
->lock held, but not with the srcu_data structure's ->lock. This is
problematic because this function accesses and updates the srcu_data
structure's ->srcu_cblist, which is protected by that lock. Failing to
hold this lock can result in corruption of the SRCU callback lists,
which in turn can result in arbitrarily bad results.
This commit therefore makes srcu_gp_start() acquire the srcu_data
structure's ->lock across the calls to rcu_segcblist_advance() and
rcu_segcblist_accelerate(), thus preventing this corruption.
Reported-by: Bart Van Assche <bvanassche@acm.org> Reported-by: Christoph Hellwig <hch@infradead.org> Reported-by: Sebastian Kuzminsky <seb.kuzminsky@gmail.com> Signed-off-by: Dennis Krein <Dennis.Krein@netapp.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Dennis Krein <Dennis.Krein@netapp.com> Cc: <stable@vger.kernel.org> # 4.16.x
Now that call_rcu()'s callback is not invoked until after all
preempt-disable regions of code have completed (in addition to explicitly
marked RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_sched(). This commit therefore makes that change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
slab: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: <linux-mm@kvack.org>
percpu-refcount: Replace call_rcu_sched() with call_rcu()
Now that call_rcu()'s callback is not invoked until after all
preempt-disable regions of code have completed (in addition to explicitly
marked RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_sched(). This commit therefore makes that change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Ming Lei <ming.lei@redhat.com> Cc: Bart Van Assche <bvanassche@acm.org> Cc: Jens Axboe <axboe@kernel.dk> Acked-by: Tejun Heo <tj@kernel.org>
events: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org>
workqueue: Replace call_rcu_sched() with call_rcu()
Now that call_rcu()'s callback is not invoked until after all
preempt-disable regions of code have completed (in addition to explicitly
marked RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_sched(). This commit therefore makes that change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Acked-by: Tejun Heo <tj@kernel.org>
modules: Replace synchronize_sched() and call_rcu_sched()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can
be replaced by synchronize_rcu(). Similarly, call_rcu_sched() can be
replaced by call_rcu(). This commit therefore makes these changes.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Jessica Yu <jeyu@kernel.org>
sched/membarrier: synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org>
lockdep: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Will Deacon <will.deacon@arm.com>
kprobes: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: "David S. Miller" <davem@davemloft.net> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
main: Replace rcu_barrier_sched() with rcu_barrier()
Now that all RCU flavors have been consolidated, rcu_barrier_sched()
is but a synonym for rcu_barrier(). This commit therefore replaces
the former with the latter.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: <linux-mm@kvack.org>
tracing: Replace synchronize_sched() and call_rcu_sched()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can
be replaced by synchronize_rcu(). Similarly, call_rcu_sched() can be
replaced by call_rcu(). This commit therefore makes these changes.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: <linux-kernel@vger.kernel.org> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
fs/file: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: <linux-fsdevel@vger.kernel.org>
cpufreq/cpufreq_governor: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
cpufreq/intel_pstate: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Len Brown <lenb@kernel.org> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: <linux-pm@vger.kernel.org>
drivers/vhost: Replace synchronize_rcu_bh() with synchronize_rcu()
Now that synchronize_rcu() waits for bh-disable regions of code as well
as RCU read-side critical sections, synchronize_rcu_bh() can be replaced
by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: <kvm@vger.kernel.org> Cc: <virtualization@lists.linux-foundation.org> Cc: <netdev@vger.kernel.org>
ethernet/realtek: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Realtek linux nic maintainers <nic_swsd@realtek.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: <netdev@vger.kernel.org>
ethernet/sis: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Francois Romieu <romieu@fr.zoreil.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: <netdev@vger.kernel.org>
drivers/ipmi: Replace synchronize_sched() with synchronize_rcu()
Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <openipmi-developer@lists.sourceforge.net> Acked-by: Corey Minyard <cminyard@mvista.com>
crypto/pcrypt: Replace synchronize_rcu_bh() with synchronize_rcu()
Now that synchronize_rcu() waits for bh-disable regions of code as
well as RCU read-side critical sections, the synchronize_rcu_bh() in
pcrypt_cpumask_change_notify() can be replaced by synchronize_rcu().
This commit therefore makes this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: <linux-crypto@vger.kernel.org> Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Lance Roy [Fri, 5 Oct 2018 06:45:50 +0000 (23:45 -0700)]
KVM: arm/arm64: vgic: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements,
since it only checks if the current thread holds the lock regardless of
whether someone else does. This is also a step towards possibly removing
spin_is_locked().
Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Eric Auger <eric.auger@redhat.com> Cc: linux-arm-kernel@lists.infradead.org Cc: <kvmarm@lists.cs.columbia.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Lance Roy [Fri, 5 Oct 2018 06:45:47 +0000 (23:45 -0700)]
mm: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements,
since it only checks if the current thread holds the lock regardless of
whether someone else does. This is also a step towards possibly removing
spin_is_locked().
Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Yang Shi <yang.shi@linux.alibaba.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Jan Kara <jack@suse.cz> Cc: Shakeel Butt <shakeelb@google.com> Cc: <linux-mm@kvack.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Lance Roy [Fri, 5 Oct 2018 06:45:46 +0000 (23:45 -0700)]
locking/mutex: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements,
since it only checks if the current thread holds the lock regardless of
whether someone else does. This is also a step towards possibly removing
spin_is_locked().
Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Lance Roy [Fri, 5 Oct 2018 06:45:44 +0000 (23:45 -0700)]
userfaultfd: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements,
since it only checks if the current thread holds the lock regardless of
whether someone else does. This is also a step towards possibly removing
spin_is_locked().
Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: <linux-fsdevel@vger.kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Lance Roy [Fri, 5 Oct 2018 06:45:42 +0000 (23:45 -0700)]
smsc: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements,
since it only checks if the current thread holds the lock regardless of
whether someone else does. This is also a step towards possibly removing
spin_is_locked().
Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Steve Glendinning <steve.glendinning@shawell.net> Cc: "David S. Miller" <davem@davemloft.net> Cc: <netdev@vger.kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Lance Roy [Fri, 5 Oct 2018 06:45:41 +0000 (23:45 -0700)]
sfc: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements,
since it only checks if the current thread holds the lock regardless of
whether someone else does. This is also a step towards possibly removing
spin_is_locked().
Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Solarflare linux maintainers <linux-net-drivers@solarflare.com> Cc: Bert Kenward <bkenward@solarflare.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: <netdev@vger.kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Edward Cree <ecree@solarflare.com>
Joe Perches [Fri, 7 Sep 2018 22:26:18 +0000 (15:26 -0700)]
checkpatch: Create table of obsolete APIs and apply to RCU
This patch creates a deprecated_apis map, which allows such APIs to
be flagged with suggested replacements more compactly and straightforwardly.
It also uses this map to flag the old flavorful RCU APIs as deprecated,
suggesting their vanilla-RCU counterparts as replacements.
Signed-off-by: Joe Perches <joe@perches.com> Cc: Andy Whitcroft <apw@canonical.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Merged with earlier less-deft approach. ]
Paul E. McKenney [Mon, 29 Oct 2018 14:36:50 +0000 (07:36 -0700)]
rcu: Avoid signed integer overflow in rcu_preempt_deferred_qs()
Subtracting INT_MIN can be interpreted as unconditional signed integer
overflow, which according to the C standard is undefined behavior.
Therefore, kernel build arguments notwithstanding, it would be good to
future-proof the code. This commit therefore substitutes INT_MAX for
INT_MIN in order to avoid undefined behavior.
While in the neighborhood, this commit also creates some meaningful names
for INT_MAX and friends in order to improve readability, as suggested
by Joel Fernandes.
Reported-by: Ran Rozenstein <ranro@mellanox.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Tue, 16 Oct 2018 11:12:58 +0000 (04:12 -0700)]
rcu: Speed up expedited GPs when interrupting RCU reader
In PREEMPT kernels, an expedited grace period might send an IPI to a
CPU that is executing an RCU read-side critical section. In that case,
it would be nice if the rcu_read_unlock() directly interacted with the
RCU core code to immediately report the quiescent state. And this does
happen in the case where the reader has been preempted. But it would
also be a nice performance optimization if immediate reporting also
happened in the preemption-free case.
This commit therefore adds an ->exp_hint field to the task_struct structure's
->rcu_read_unlock_special field. The IPI handler sets this hint when
it has interrupted an RCU read-side critical section, and this causes
the outermost rcu_read_unlock() call to invoke rcu_read_unlock_special(),
which, if preemption is enabled, reports the quiescent state immediately.
If preemption is disabled, then the report is required to be deferred
until preemption (or bottom halves or interrupts or whatever) is re-enabled.
Because this is a hint, it does nothing for more complicated cases. For
example, if the IPI interrupts an RCU reader, but interrupts are disabled
across the rcu_read_unlock(), but another rcu_read_lock() is executed
before interrupts are re-enabled, the hint will already have been cleared.
If you do crazy things like this, reporting will be deferred until some
later RCU_SOFTIRQ handler, context switch, cond_resched(), or similar.
Reported-by: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Paul E. McKenney [Mon, 15 Oct 2018 17:00:58 +0000 (10:00 -0700)]
rcu: Trace end of grace period before end of grace period
Currently, rcu_gp_cleanup() traces the end of the old grace period after
the old grace period has officially ended. This might make intuitive
sense, but it also makes for confusing event-trace output because the
"end" trace displays not the old but instead the new grace-period number.
This commit therefore traces the end of an old grace period just before
that grace period officially ends.
Reported-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Zhouyi Zhou [Mon, 8 Oct 2018 06:50:41 +0000 (06:50 +0000)]
rcu: Adjust the comment of function rcu_is_watching
Because RCU avoids interrupting idle CPUs, rcu_is_watching() is used to
test whether or not it is currently legal to run RCU read-side critical
sections on this CPU. However, the first sentence and last sentences
of current comment for rcu_is_watching have opposite meaning of what
is expected. This commit therefore fixes this header comment.
Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
rcu: Add jiffies-since-GP-activity to show_rcu_gp_kthreads()
This commit adds a printout of the number of jiffies since the last time
that the RCU grace-period kthread did any processing. This can be useful
when tracking down forward-progress issues.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
rcu: Add state name to show_rcu_gp_kthreads() output
This commit adds the name of the RCU grace-period state to
the show_rcu_gp_kthreads() output in order to ease debugging.
This commit also moves gp_state_getname() up in the code so that
show_rcu_gp_kthreads() can use it.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
In order to debug forward-progress stalls, it is necessary to check
for excessively delayed grace-period starts. This is currently done
for RCU CPU stall warnings by rcu_check_gp_start_stall(), which checks
to see if the start of a requested grace period has been delayed by an
RCU CPU stall warning period. Because rcutorture will need to check
for the time consumed by an RCU forward-progress delay, this commit
promotes gpssdelay from a local variable to a formal parameter. It is
not necessary to export rcu_check_gp_start_stall() because rcutorture
will access it via a wrapper function.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
The rcu_check_gp_start_stall() function multiplies the return value
from rcu_jiffies_till_stall_check() by HZ, but the units are already
in jiffies. This commit therefore avoids the need for introduction of
a jiffies-squared unit by removing the extraneous multiplication.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Fri, 14 Sep 2018 16:50:11 +0000 (09:50 -0700)]
MAINTAINERS: Update from @linux.vnet.ibm.com to @linux.ibm.com
IBM's patch-friendly email infrastructure is changing domains from
@linux.vnet.ibm.com to @linux.ibm.com, which if nothing else might
save a bit of typing. This commit therefore updates us stragglers'
email addresses in the MAINTAINERS file. The old addresses are
expected to continue to work for a few more months.
While in the neighborhood, remove some obsolete entries, which results
in an orphaned subsystem: "JSM Neo PCI based serial card".
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Douglas Miller <dougmill@linux.ibm.com> Cc: Eddie James <eajames@linux.ibm.com> Cc: Frank Haverkamp <haver@linux.ibm.com> Cc: Frederic Barrat <fbarrat@linux.ibm.com> Cc: John Allen <jallen@linux.ibm.com> Cc: Manoj N. Kumar <manoj@linux.ibm.com> Cc: Matthew R. Ochs <mrochs@linux.ibm.com> Cc: Michael Cyr <mikecyr@linux.ibm.com> Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com> Cc: Paulo Flabiano Smorigo <pfsmorigo@linux.ibm.com> Cc: Philip Kelleher <pjk1939@linux.ibm.com> Cc: Steven Royer <seroyer@linux.ibm.com> Cc: Thomas Falcon <tlfalcon@linux.ibm.com> Cc: Tyrel Datwyler <tyreld@linux.ibm.com> Cc: Uma Krishnan <ukrishn@linux.ibm.com> Acked-by: James Bottomley <jejb@linux.ibm.com> Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Given RCU flavor consolidation, when rcu_read_unlock() is invoked with
interrupts disabled, the reporting of the corresponding quiescent state is
deferred until interrupts are re-enabled. There was therefore some hope
that this would allow dropping the restriction against holding scheduler
spinlocks across an rcu_read_unlock() without disabling interrupts across
the entire corresponding RCU read-side critical section. Unfortunately,
the need to quickly provide a quiescent state to expedited grace periods
sometimes requires a call to raise_softirq() during rcu_read_unlock()
execution. Because raise_softirq() can sometimes acquire the scheduler
spinlocks, the restriction must remain in effect. This commit therefore
updates the RCU requirements documentation accordingly.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: Make listing in RCU perf/scale requirements use rcu_assign_pointer()
The code listing under this section has a quick quiz that says line
19 uses rcu_access_pointer, but the code listing itself instead uses
rcu_dereference(). This commit therefore makes the code listing match
the quick quiz.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: Remove obsolete (non-)requirement about disabling preemption
The Requirements.html document says "Disabling Preemption Does
Not Block Grace Periods". However this is no longer true with
the RCU consolidation. This commit therefore removes the obsolete
(non-)requirement entirely.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: Make reader aware of rcu_dereference_protected
The whatisRCU.txt document says rcu_dereference() cannot be used
outside of rcu_read_lock() protected sections. The commit adds a
mention of rcu_dereference_protected(), so that the new reader knows
that this API can be used to avoid update-side use of rcu_read_lock()
and rcu_read_unlock().
Cc: tytso@mit.edu Suggested-by: tytso@mit.edu Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Update wording, including further feedback from Joel. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: rcu: Encourage use of rcu_barrier in checklist
The checklist suggests rcu_barrier_bh() for RCU-bh and similarly for
sched, however these APIs are now implemented as rcu_barrier() itself due
to the RCU consolidation. This commit therefore corrects checklist.txt
to encourage use of the underlying rcu_barrier() API.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: rcu: Remove obsolete checklist item about synchronize_rcu usage
Since the RCU mechanisms have been consolidated, the checklist item
warning that synchronize_rcu() waits only for RCU readers is obsolete.
This commit therefore removes this checklist item.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: rcu: Remove obsolete suggestion from checklist
call_rcu_bh is now implemented in terms of call_rcu, so the suggestion
to use a different API for speed benefits is not accurate anymore.
This commit updates the document accordingly.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
RCU consolidation effort causes the update side of the RCU API to
be consistent across all the 3 RCU flavors (normal, sched, bh). This
commit therefore updates the full API in the whatisRCU document, thus
encouraging people to use the consolidated RCU update API instead of
the old RCU-bh and RCU-sched update APIs.
Also rcu_dereference is documented to be the same for all 3 mechanisms
(even before the consolidation), however its actually different - as
using the right rcu_dereference primitive (such as rcu_dereference_bh
for bh) is needed to make lock debugging work correctly. This update
also corrects that.
Also, add local_bh_disable() and local_bh_enable() as softirq
protection primitives and correct a grammar error in a quiz answer.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: rcu: Better clarify the rcu_segcblist ->len field
An important note under the rcu_segcblist description could use a more
detailed description. Especially explanation of the scenario where the
->head field may be temporarily NULL making it not wise to rely on it
to determine if callbacks are associated with the rcu_segcblist.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: rcu: Update Data-Structures for RCU flavor consolidation
This patch updates all Data-Structures document figures and text and
removes some unwanted figures, to reflect the recent work Paul has been
doing with consolidating all flavors of RCU.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Since commit fced9c8cfe6b ("rcu: Avoid resched_cpu() when rescheduling
the current CPU"), resched_cpu is not directly called from
sync_sched_exp_handler. Update the documentation about the same.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Mon, 22 Oct 2018 15:33:06 +0000 (08:33 -0700)]
rcu: Eliminate BUG_ON() for kernel/rcu/update.c
The update.c file has a number of calls to BUG_ON(), which panics the
kernel, which is not a good strategy for devices (like embedded) that
don't have a way to capture console output. This commit therefore
converts these BUG_ON() calls to WARN_ON_ONCE() and WARN_ONCE().
Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Mon, 22 Oct 2018 15:26:00 +0000 (08:26 -0700)]
rcu: Eliminate BUG_ON() for kernel/rcu/tree_plugin.h
The tree_plugin.h file has a number of calls to BUG_ON(), which panics
the kernel, which is not a good strategy for devices (like embedded)
that don't have a way to capture console output. This commit therefore
converts these BUG_ON() calls to WARN_ON_ONCE() and WARN_ONCE().
Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Fix typo: s/rcuo/rcub/. ]
Paul E. McKenney [Tue, 11 Sep 2018 15:57:48 +0000 (08:57 -0700)]
rcu: Stop expedited grace periods from relying on stop-machine
The CPU-selection code in sync_rcu_exp_select_cpus() disables preemption
to prevent the cpu_online_mask from changing. However, this relies on
the stop-machine mechanism in the CPU-hotplug offline code, which is not
desirable (it would be good to someday remove the stop-machine mechanism).
This commit therefore instead uses the relevant leaf rcu_node structure's
->ffmask, which has a bit set for all CPUs that are fully functional.
A given CPU's bit is cleared very early during offline processing by
rcutree_offline_cpu() and set very late during online processing by
rcutree_online_cpu(). Therefore, if a CPU's bit is set in this mask, and
preemption is disabled, we have to be before the synchronize_sched() in
the CPU-hotplug offline code, which means that the CPU is guaranteed to be
workqueue-ready throughout the duration of the enclosing preempt_disable()
region of code.
This also has the side-effect of using WORK_CPU_UNBOUND if all the CPUs for
this leaf rcu_node structure are offline, which is an acceptable difference
in behavior.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Paul E. McKenney [Wed, 25 Apr 2018 20:01:25 +0000 (13:01 -0700)]
srcu: Prevent __call_srcu() counter wrap with read-side critical section
Ever since cdf7abc4610a ("srcu: Allow use of Tiny/Tree SRCU from
both process and interrupt context"), it has been permissible
to use SRCU read-side critical sections in interrupt context.
This allows __call_srcu() to use SRCU read-side critical sections to
prevent a new SRCU grace period from ending before the call to either
srcu_funnel_gp_start() or srcu_funnel_exp_start completes, thus preventing
SRCU grace-period counter overflow during that time.
Note that this does not permit removal of the counter-wrap checks in
srcu_gp_end(). These check are necessary to handle the case where
a given CPU does not interact at all with SRCU for an extended time
period.
This commit therefore adds an SRCU read-side critical section to
__call_srcu() in order to prevent grace period counter wrap during
the funnel-locking process.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Randy Dunlap [Mon, 3 Sep 2018 19:45:45 +0000 (12:45 -0700)]
srcu: Fix kernel-doc missing notation
Fix kernel-doc warnings for missing parameter descriptions:
../include/linux/srcu.h:175: warning: Function parameter or member 'p' not described in 'srcu_dereference_notrace'
../include/linux/srcu.h:175: warning: Function parameter or member 'sp' not described in 'srcu_dereference_notrace'
Fixes: 0b764a6e4e19d ("srcu: Add notrace variant of srcu_dereference") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Lance Roy [Fri, 5 Oct 2018 06:45:38 +0000 (23:45 -0700)]
x86/PCI: Replace spin_is_locked() with lockdep
lockdep_assert_held() is better suited to checking locking requirements,
since it only checks if the current thread holds the lock regardless of
whether someone else does. This is also a step towards possibly removing
spin_is_locked().
Signed-off-by: Lance Roy <ldr709@gmail.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: <x86@kernel.org> Cc: <linux-pci@vger.kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This reduces the size of the init executable from ~800 kB to ~800 bytes
on x86_64. This is only implemented for x86_64, i386, arm and arm64.
Others not tested.
Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This is a definition of the most common syscalls needed in minimalist
init executables, allowing to statically build them with no external
dependencies. It is sufficient in its current form to build rcutorture's
init on x86_64, i386, arm, and arm64. Others have not been ported or
tested. Updates may be found here :
rcutorture: Check initrd/init instead of initrd only
If the build fails, we can end up with an empty initrd directory which
prevents the build script from operating again. Better rely on the
resulting init executable instead.
Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Paul E. McKenney [Thu, 23 Aug 2018 22:23:23 +0000 (15:23 -0700)]
rcutorture: Make initrd/init execute in userspace
Currently, the initrd/init script and executable remain blocked almost
all the time. However, it is necessary to test nohz_full userspace
execution, which both variants of initrd/init fail to do. This commit
therefore causes initrd/init to spend about a millisecond per second
executing in userspace.
Reported-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Paul E. McKenney [Thu, 23 Aug 2018 17:48:18 +0000 (10:48 -0700)]
rcutorture: Add initrd support for systems lacking dracut
The support for creating initrd directories using dracut is a great
improvement over having to always hand-create them, it is a bit annoying
to have to install some otherwise irrelevant package just to be able to
run rcutorture. This commit therefore adds support for creating initrd
directories on systems innocent of dracut. You do need gcc, but then
again you need that to build the kernel (or to build llvm) in any case.
The idea is to create an initrd directory containing nothing but a
statically linked binary having a for-loop over a long-term sleep().
The result is a Linux kernel with almost no userspace: even the
time-honored /dev, /lib, /tmp, and /usr directories are gone. In fact,
the only directory present is "/", but only because I don't know how to
get rid of it, at least short of not having an initrd in the first place.
Although statically linked binaries are much maligned, and rightly so,
their disadvantages seem to be irrelevant for this particular use case.
From https://www.akkadia.org/drepper/no_static_linking.html:
1. Fixes are difficult to apply to hordes of widely scattered
statically linked binaries. But in this case, there is only one
binary, but there would otherwise be no fewer than four libraries.
2. Security measures like local address randomization cannot be used.
Prudence prevents me from asserting that it is impossible to
base a remote attack on a networking-free rcutorture instance.
Nevertheless, bonus points to the first person who comes up with
such an attack!
3. More efficient use of physical memory. Not in this case, given
that libc is 1.8MB and the statically linked binary "only" 800K.
4. Features such as locales, name service switch (NSS),
internationalized domain names (IDN) tool, and so on require
dynamic linking. Bonus points to the first person coming up
with a valid rcutorture use case requiring these features in
its initrd.
5. Accidental violations of (L)GPL. Actually, this change actually
helps -avoid- such violations by reducing the temptation to
pass around tarballs of rcutorture-ready initrd directories.
After all, the rcutorture scripts automatically create an initrd
directory for you, so why bother with the tarballs?
6. Tools and hacks like ltrace, LD_PRELOAD, LD_PROFILE, and LD_AUDIT
don't work. Again, bonus points to the first person coming up
with a valid rcutorture use case requiring these features in
its initrd.
Nevertheless, the script will use dracut if available, and will create the
statically linked binary only when dracut are missing. Those preferring
the smaller initrd directory resulting from the statically linked binary
(like me) are free to hand-edit mkinitrd.sh to remove the code using
dracut. ;-)
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Connor Shu [Wed, 22 Aug 2018 21:16:46 +0000 (14:16 -0700)]
rcutorture: Automatically create initrd directory
The rcutorture scripts currently expect the user to create the
tools/testing/selftests/rcutorture/initrd directory. Should the user
fail to do this, the kernel build will fail with obscure and confusing
error messages. This commit therefore adds explicit checks for the
tools/testing/selftests/rcutorture/initrd directory, and if not present,
creates one on systems on which dracut is installed. If this directory
could not be created, a less obscure error message is emitted and the
test is aborted.
Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Connor Shu <Connor.Shu@ibm.com>
[ paulmck: Adapt the script to fit into the rcutorture framework and
severely abbreviate the initrd/init script. ] Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
doc: Remove rcu_preempt_state reference in stallwarn
Consolidation of RCU-bh, RCU-preempt, and RCU-sched into one RCU flavor
to rule them all resulted in the removal of rcu_preempt_state. However,
stallwarn.txt still mentions rcu_preempt_state. This commit therefore
Updates stallwarn documentation accordingly.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: Clarify RCU data-structure comment about rcu_tree fanout
RCU Data-Structures document describes a trick to test RCU with small
number of CPUs but with a taller tree. It wasn't immediately clear how
the document arrived at 16 CPUs which also requires setting the
FANOUT_LEAF to 2 instead of the default of 16. This commit therefore
provides the needed clarification.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Now that call_rcu()'s callback is not invoked until after all
preempt-disable regions of code have completed (in addition to explicitly
marked RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_sched(). This commit therefore makes that change.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: <linuxppc-dev@lists.ozlabs.org>