panic: fix a possible deadlock in panic()
authorVikram Mulukutla <markivx@codeaurora.org>
Mon, 30 Jul 2012 21:39:58 +0000 (14:39 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 12 Apr 2013 16:38:47 +0000 (09:38 -0700)
commit5592a94b44df6e6d48e34cfe596844637a2976ac
tree75de4b4f29df40c505eefb9627a4149c5a66b125
parentddcd89f15f9e85d5cd37c866a1c5da9a3ca204d1
panic: fix a possible deadlock in panic()

commit 190320c3b6640d4104650f55ff69611e050ea06b upstream.

panic_lock is meant to ensure that panic processing takes place only on
one cpu; if any of the other cpus encounter a panic, they will spin
waiting to be shut down.

However, this causes a regression in this scenario:

1. Cpu 0 encounters a panic and acquires the panic_lock
   and proceeds with the panic processing.
2. There is an interrupt on cpu 0 that also encounters
   an error condition and invokes panic.
3. This second invocation fails to acquire the panic_lock
   and enters the infinite while loop in panic_smp_self_stop.

Thus all panic processing is stopped, and the cpu is stuck for eternity
in the while(1) inside panic_smp_self_stop.

To address this, disable local interrupts with local_irq_disable before
acquiring the panic_lock.  This will prevent interrupt handlers from
executing during the panic processing, thus avoiding this particular
problem.

Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/panic.c