Messages in this thread | | | Subject | Re: [x86/signal] 3aac3ebea0: will-it-scale.per_thread_ops -11.9% regression | From | Dave Hansen <> | Date | Wed, 8 Dec 2021 10:20:26 -0800 |
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On 12/8/21 10:00 AM, Bae, Chang Seok wrote: > diff --git a/kernel/signal.c b/kernel/signal.c > index a629b11bf3e0..8194d2f38bf1 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -4224,6 +4224,11 @@ int restore_altstack(const stack_t __user *uss) > stack_t new; > if (copy_from_user(&new, uss, sizeof(stack_t))) > return -EFAULT; > + if (current->sas_ss_sp == (unsigned long) new.ss_sp && > + current->sas_ss_size == new.ss_size && > + current->sas_ss_flags == new.ss_flags) > + return 0; > + > (void)do_sigaltstack(&new, NULL, current_user_stack_pointer(), > MINSIGSTKSZ); > /* squash all but EFAULT for now */
This seems like a generally good optimization that could go in do_sigaltstack() itself, no?
Either way, it seems like 0day botched this a bit. '3aac3ebea0' wasn't the actual culprit, it was the patch before.
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