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authorVikram Mulukutla <markivx@codeaurora.org>2012-07-30 14:39:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-30 17:25:13 -0700
commit190320c3b6640d4104650f55ff69611e050ea06b (patch)
tree94d43c11e025e4b4efc577a2cf88a29250d4f510 /kernel
parent6c55845e71ba7a862395f504a240a5b62632e0d6 (diff)
panic: fix a possible deadlock in panic()
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/panic.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/panic.c b/kernel/panic.c
index d2a5f4ecc6dd..e1b2822fff97 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -75,6 +75,14 @@ void panic(const char *fmt, ...)
int state = 0;
/*
+ * Disable local interrupts. This will prevent panic_smp_self_stop
+ * from deadlocking the first cpu that invokes the panic, since
+ * there is nothing to prevent an interrupt handler (that runs
+ * after the panic_lock is acquired) from invoking panic again.
+ */
+ local_irq_disable();
+
+ /*
* It's possible to come here directly from a panic-assertion and
* not have preempt disabled. Some functions called from here want
* preempt to be disabled. No point enabling it later though...