> From: Peter Zijlstra [mailto:pet...@infradead.org]
>
> 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?
What part are you arguing? Recursive call of crash_kexec() doesn't
happen. In the first place, one of the purpose of this patch is
to prevent a recursive call of crash_kexec() in the following case
as I stated in the description:
CPU 0:
oops_end()
crash_kexec()
mutex_trylock() // acquired
<NMI>
io_check_error()
panic()
crash_kexec()
mutex_trylock() // failed to acquire
infinite loop
Also, the logic doesn't change form V1 (although the implementation
changed), so I didn't add changelogs any more.
Regards,
Hidehiro Kawai
Hitachi, Ltd. Research & Development Group
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