On 11/14/23 at 05:12pm, Uros Bizjak wrote: > Use atomic_try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in > crash_kexec(). x86 CMPXCHG instruction returns success in ZF flag, > so this change saves a compare after cmpxchg. > > No functional change intended.
And code is simplified a little bit, so looks good to me, Acked-by: Baoquan He <[email protected]> > > Cc: Eric Biederman <[email protected]> > Signed-off-by: Uros Bizjak <[email protected]> > --- > kernel/kexec_core.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > index be5642a4ec49..bc4c096ab1f3 100644 > --- a/kernel/kexec_core.c > +++ b/kernel/kexec_core.c > @@ -1063,9 +1063,10 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs) > * panic(). Otherwise parallel calls of panic() and crash_kexec() > * may stop each other. To exclude them, we use panic_cpu here too. > */ > + old_cpu = PANIC_CPU_INVALID; > this_cpu = raw_smp_processor_id(); > - old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu); > - if (old_cpu == PANIC_CPU_INVALID) { > + > + if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) { > /* This is the 1st CPU which comes here, so go ahead. */ > __crash_kexec(regs); > > -- > 2.41.0 > > > _______________________________________________ > kexec mailing list > [email protected] > http://lists.infradead.org/mailman/listinfo/kexec > _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
