• Daniel Thompson's avatar
    ARM: 8439/1: Fix backtrace generation when IPI is masked · 0768330d
    Daniel Thompson authored
    Currently on ARM when <SysRq-L> is triggered from an interrupt handler
    (e.g. a SysRq issued using UART or kbd) the main CPU will wedge for ten
    seconds with interrupts masked before issuing a backtrace for every CPU
    except itself.
    
    The new backtrace code introduced by commit 96f0e003 ("ARM: add
    basic support for on-demand backtrace of other CPUs") does not work
    correctly when run from an interrupt handler because IPI_CPU_BACKTRACE
    is used to generate the backtrace on all CPUs but cannot preempt the
    current calling context.
    
    This can be fixed by detecting that the calling context cannot be
    preempted and issuing the backtrace directly in this case. Issuing
    directly leaves us without any pt_regs to pass to nmi_cpu_backtrace()
    so we also modify the generic code to call dump_stack() when its
    argument is NULL.
    Acked-by: default avatarHillf Danton <hillf.zj@alibaba-inc.com>
    Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarDaniel Thompson <daniel.thompson@linaro.org>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    0768330d
smp.c 17.1 KB