From: Srivatsa S. Bhat Date: Wed, 20 Mar 2013 10:01:29 +0000 (+0530) Subject: x86/mce: Rework cmci_rediscover() to play well with CPU hotplug X-Git-Tag: v3.10-rc1~162^2~1^2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=7a0c819d28f5c91955854e048766d6afef7c8a3d;p=linux.git x86/mce: Rework cmci_rediscover() to play well with CPU hotplug Dave Jones reports that offlining a CPU leads to this trace: numa_remove_cpu cpu 1 node 0: mask now 0,2-3 smpboot: CPU 1 is now offline BUG: using smp_processor_id() in preemptible [00000000] code: cpu-offline.sh/10591 caller is cmci_rediscover+0x6a/0xe0 Pid: 10591, comm: cpu-offline.sh Not tainted 3.9.0-rc3+ #2 Call Trace: [] debug_smp_processor_id+0xdd/0x100 [] cmci_rediscover+0x6a/0xe0 [] mce_cpu_callback+0x19d/0x1ae [] notifier_call_chain+0x66/0x150 [] __raw_notifier_call_chain+0xe/0x10 [] cpu_notify+0x23/0x50 [] cpu_notify_nofail+0xe/0x20 [] _cpu_down+0x302/0x350 [] cpu_down+0x36/0x50 [] store_online+0x8d/0xd0 [] dev_attr_store+0x18/0x30 [] sysfs_write_file+0xdb/0x150 [] vfs_write+0xa2/0x170 [] sys_write+0x4c/0xa0 [] system_call_fastpath+0x16/0x1b However, a look at cmci_rediscover shows that it can be simplified quite a bit, apart from solving the above issue. It invokes functions that take spin locks with interrupts disabled, and hence it can run in atomic context. Also, it is run in the CPU_POST_DEAD phase, so the dying CPU is already dead and out of the cpu_online_mask. So take these points into account and simplify the code, and thereby also fix the above issue. Reported-by: Dave Jones Signed-off-by: Srivatsa S. Bhat Signed-off-by: Tony Luck --- diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h index f4076af1f4ed..fa5f71e021d5 100644 --- a/arch/x86/include/asm/mce.h +++ b/arch/x86/include/asm/mce.h @@ -146,13 +146,13 @@ DECLARE_PER_CPU(struct device *, mce_device); void mce_intel_feature_init(struct cpuinfo_x86 *c); void cmci_clear(void); void cmci_reenable(void); -void cmci_rediscover(int dying); +void cmci_rediscover(void); void cmci_recheck(void); #else static inline void mce_intel_feature_init(struct cpuinfo_x86 *c) { } static inline void cmci_clear(void) {} static inline void cmci_reenable(void) {} -static inline void cmci_rediscover(int dying) {} +static inline void cmci_rediscover(void) {} static inline void cmci_recheck(void) {} #endif diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 7bc126346ace..9239504b41cb 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -2358,7 +2358,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) if (action == CPU_POST_DEAD) { /* intentionally ignoring frozen here */ - cmci_rediscover(cpu); + cmci_rediscover(); } return NOTIFY_OK; diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c index 402c454fbff0..ae1697c2afe3 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_intel.c +++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c @@ -285,39 +285,24 @@ void cmci_clear(void) raw_spin_unlock_irqrestore(&cmci_discover_lock, flags); } -static long cmci_rediscover_work_func(void *arg) +static void cmci_rediscover_work_func(void *arg) { int banks; /* Recheck banks in case CPUs don't all have the same */ if (cmci_supported(&banks)) cmci_discover(banks); - - return 0; } -/* - * After a CPU went down cycle through all the others and rediscover - * Must run in process context. - */ -void cmci_rediscover(int dying) +/* After a CPU went down cycle through all the others and rediscover */ +void cmci_rediscover(void) { - int cpu, banks; + int banks; if (!cmci_supported(&banks)) return; - for_each_online_cpu(cpu) { - if (cpu == dying) - continue; - - if (cpu == smp_processor_id()) { - cmci_rediscover_work_func(NULL); - continue; - } - - work_on_cpu(cpu, cmci_rediscover_work_func, NULL); - } + on_each_cpu(cmci_rediscover_work_func, NULL, 1); } /*