Messages in this thread | | | Date | Tue, 29 May 2012 13:53:53 -0400 | From | Don Zickus <> | Subject | Re: [PATCH] x86: Avoid intermixing cpu dump_stack output on multi-processor systems |
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On Thu, May 24, 2012 at 09:42:29AM -0500, Russ Anderson wrote: > When multiple cpus on a multi-processor system call dump_stack() > at the same time, the backtrace lines get intermixed, making > the output worthless. Add a lock so each cpu stack dump comes > out as a coherent set. > > For example, when a multi-processor system is NMIed, all of the > cpus call dump_stack() at the same time, resulting in output for > all of cpus getting intermixed, making it impossible to tell what > any individual cpu was doing. With this patch each cpu prints > its stack lines as a coherent set, so one can see what each cpu > was doing.
For this particular test case, it sounds like you are doing what trigger_all_cpu_backtrace() is doing? It doesn't solve the general problem, but probably your particular usage?
Cheers, Don
> > It has been tested on a 4069 cpu system. > > Signed-off-by: Russ Anderson <rja@sgi.com> > > --- > arch/x86/kernel/dumpstack.c | 3 +++ > 1 file changed, 3 insertions(+) > > Index: linux/arch/x86/kernel/dumpstack.c > =================================================================== > --- linux.orig/arch/x86/kernel/dumpstack.c 2012-05-03 14:31:13.602345805 -0500 > +++ linux/arch/x86/kernel/dumpstack.c 2012-05-03 14:51:43.805197563 -0500 > @@ -186,7 +186,9 @@ void dump_stack(void) > { > unsigned long bp; > unsigned long stack; > + static DEFINE_SPINLOCK(lock); /* Serialise the printks */ > > + spin_lock(&lock); > bp = stack_frame(current, NULL); > printk("Pid: %d, comm: %.20s %s %s %.*s\n", > current->pid, current->comm, print_tainted(), > @@ -194,6 +196,7 @@ void dump_stack(void) > (int)strcspn(init_utsname()->version, " "), > init_utsname()->version); > show_trace(NULL, NULL, &stack, bp); > + spin_unlock(&lock); > } > EXPORT_SYMBOL(dump_stack); > > -- > Russ Anderson, OS RAS/Partitioning Project Lead > SGI - Silicon Graphics Inc rja@sgi.com > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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