Commit 190320c3b6640d4104650f55ff69611e050ea06b
Committed by
Linus Torvalds
1 parent
6c55845e71
Exists in
master
and in
20 other branches
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>
Showing 1 changed file with 8 additions and 0 deletions Side-by-side Diff
kernel/panic.c
... | ... | @@ -75,6 +75,14 @@ |
75 | 75 | int state = 0; |
76 | 76 | |
77 | 77 | /* |
78 | + * Disable local interrupts. This will prevent panic_smp_self_stop | |
79 | + * from deadlocking the first cpu that invokes the panic, since | |
80 | + * there is nothing to prevent an interrupt handler (that runs | |
81 | + * after the panic_lock is acquired) from invoking panic again. | |
82 | + */ | |
83 | + local_irq_disable(); | |
84 | + | |
85 | + /* | |
78 | 86 | * It's possible to come here directly from a panic-assertion and |
79 | 87 | * not have preempt disabled. Some functions called from here want |
80 | 88 | * preempt to be disabled. No point enabling it later though... |