• Vikram Mulukutla's avatar
    panic: fix a possible deadlock in panic() · 190320c3
    Vikram Mulukutla authored
    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: default avatarVikram Mulukutla <markivx@codeaurora.org>
    Reviewed-by: default avatarStephen Boyd <sboyd@codeaurora.org>
    Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    190320c3
panic.c 11.2 KB