rcu/x86: Provide early rcu_cpu_starting() callback

The x86/mtrr code does horrific things because hardware. It uses
stop_machine_from_inactive_cpu(), which does a wakeup (of the stopper
thread on another CPU), which uses RCU, all before the CPU is onlined.

RCU complains about this, because wakeups use RCU and RCU does
(rightfully) not consider offline CPUs for grace-periods.

Fix this by initializing RCU way early in the MTRR case.

Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Add !SMP support, per 0day Test Robot report. ]

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 7468de4290873ad4664a5575e6cc0f4d74a26ae6..3ea0047beb40d3eea5de2f71d063ce07471392a5 100644 (file)
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -46,6 +46,7 @@
 #include <linux/pci.h>
 #include <linux/smp.h>
 #include <linux/syscore_ops.h>
+#include <linux/rcupdate.h>
 
 #include <asm/cpufeature.h>
 #include <asm/e820/api.h>
@@ -793,6 +794,9 @@ void mtrr_ap_init(void)
 
        if (!use_intel() || mtrr_aps_delayed_init)
                return;
+
+       rcu_cpu_starting(smp_processor_id());
+
        /*
         * Ideally we should hold mtrr_mutex here to avoid mtrr entries
         * changed, but this routine will be called in cpu boot time,

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 19d235fefdb91b6af8529116831e5d4a76cbf5ad..e679b175b41105a0c052889a079fe32cd2eeb9c3 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -108,7 +108,6 @@ void rcu_sched_qs(void);
 void rcu_bh_qs(void);
 void rcu_check_callbacks(int user);
 void rcu_report_dead(unsigned int cpu);
-void rcu_cpu_starting(unsigned int cpu);
 void rcutree_migrate_callbacks(int cpu);
 
 #ifdef CONFIG_RCU_STALL_COMMON

diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index ce9beec35e34a512fa76069124b2de83daaf6068..7b3c82e8a625dcdb421bd0f2ac97316e3fd1d4be 100644 (file)
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -132,5 +132,6 @@ static inline void rcu_all_qs(void) { barrier(); }
 #define rcutree_offline_cpu      NULL
 #define rcutree_dead_cpu         NULL
 #define rcutree_dying_cpu        NULL
+static inline void rcu_cpu_starting(unsigned int cpu) { }
 
 #endif /* __LINUX_RCUTINY_H */

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 448f20f27396526f5f0970de0a4629001e136fcd..914655848ef6a940bd343799e9f350fc7b9a8639 100644 (file)
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -101,5 +101,6 @@ int rcutree_online_cpu(unsigned int cpu);
 int rcutree_offline_cpu(unsigned int cpu);
 int rcutree_dead_cpu(unsigned int cpu);
 int rcutree_dying_cpu(unsigned int cpu);
+void rcu_cpu_starting(unsigned int cpu);
 
 #endif /* __LINUX_RCUTREE_H */

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4fccdfa25716c6b09f1545e717c3e0b429e20a15..aa7cade1b9f399abcac792e08a97114305a241ad 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3665,6 +3665,8 @@ int rcutree_dead_cpu(unsigned int cpu)
        return 0;
 }
 
+static DEFINE_PER_CPU(int, rcu_cpu_started);
+
 /*
  * Mark the specified CPU as being online so that subsequent grace periods
  * (both expedited and normal) will wait on it.  Note that this means that
@@ -3686,6 +3688,11 @@ void rcu_cpu_starting(unsigned int cpu)
        struct rcu_node *rnp;
        struct rcu_state *rsp;
 
+       if (per_cpu(rcu_cpu_started, cpu))
+               return;
+
+       per_cpu(rcu_cpu_started, cpu) = 1;
+
        for_each_rcu_flavor(rsp) {
                rdp = per_cpu_ptr(rsp->rda, cpu);
                rnp = rdp->mynode;
@@ -3742,6 +3749,8 @@ void rcu_report_dead(unsigned int cpu)
        preempt_enable();
        for_each_rcu_flavor(rsp)
                rcu_cleanup_dying_idle_cpu(cpu, rsp);
+
+       per_cpu(rcu_cpu_started, cpu) = 0;
 }
 
 /* Migrate the dead CPU's callbacks to the current CPU. */