lkml.org 
[lkml]   [2012]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86: Avoid intermixing cpu dump_stack output on multi-processor systems
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/


\
 
 \ /
  Last update: 2012-05-29 20:41    [W:0.089 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site