From f94b61c2c9fdcc90773c49df9ccf9ede3ad0d7db Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Wed, 27 May 2009 21:56:55 +0200 Subject: [PATCH] x86, mce: implement panic synchronization In some circumstances multiple CPUs can enter mce_panic() in parallel. This gives quite confused output because they will all dump the same machine check buffer. The other problem is that they would all panic in parallel, but not process each other's shutdown IPIs because interrupts are disabled. Detect this situation early on in mce_panic(). On the first CPU entering will do the panic, the others will just wait to be killed. For paranoia reasons in case the other CPU dies during the MCE I added a 5 seconds timeout. If it expires each CPU will panic on its own again. Signed-off-by: Andi Kleen Signed-off-by: Hidetoshi Seto Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/mcheck/mce.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 121781627858..421020f1d7db 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -196,10 +196,32 @@ static void print_mce(struct mce *m) "and contact your hardware vendor\n"); } +#define PANIC_TIMEOUT 5 /* 5 seconds */ + +static atomic_t mce_paniced; + +/* Panic in progress. Enable interrupts and wait for final IPI */ +static void wait_for_panic(void) +{ + long timeout = PANIC_TIMEOUT*USEC_PER_SEC; + preempt_disable(); + local_irq_enable(); + while (timeout-- > 0) + udelay(1); + panic("Panicing machine check CPU died"); +} + static void mce_panic(char *msg, struct mce *final, char *exp) { int i; + /* + * Make sure only one CPU runs in machine check panic + */ + if (atomic_add_return(1, &mce_paniced) > 1) + wait_for_panic(); + barrier(); + bust_spinlocks(1); console_verbose(); /* First print corrected ones that are still unlogged */