[V3 PATCH 3/4] kexec: Fix race between panic() and crash_kexec() called directly
peterz at infradead.org
Thu Aug 20 16:08:45 PDT 2015
On Thu, Aug 06, 2015 at 02:45:43PM +0900, Hidehiro Kawai wrote:
> void crash_kexec(struct pt_regs *regs)
> + int old_cpu, this_cpu;
> + /*
> + * `old_cpu == -1' means we are the first comer and crash_kexec()
> + * was called without entering panic().
> + * `old_cpu == this_cpu' means crash_kexec() was called from panic().
> + */
> + this_cpu = raw_smp_processor_id();
> + old_cpu = atomic_cmpxchg(&panic_cpu, -1, this_cpu);
> + if (old_cpu != -1 && old_cpu != this_cpu)
> + return;
This allows recursive calling of crash_kexec(), the Changelog did not
mention that. Is this really required?
> /* Take the kexec_mutex here to prevent sys_kexec_load
> * running on one cpu from replacing the crash kernel
> * we are using after a panic on a different cpu.
More information about the kexec