From 7a0c819d28f5c91955854e048766d6afef7c8a3d Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Wed, 20 Mar 2013 15:31:29 +0530 Subject: 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 --- arch/x86/kernel/cpu/mcheck/mce.c | 2 +- arch/x86/kernel/cpu/mcheck/mce_intel.c | 25 +++++-------------------- 2 files changed, 6 insertions(+), 21 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 7bc126346ac..9239504b41c 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 402c454fbff..ae1697c2afe 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); } /* -- cgit v1.2.3-70-g09d2