On Sun, Apr 02, 2023 at 10:22:32PM -0700, Ankur Arora wrote: > Allow threads marked TIF_ALLOW_RESCHED to be rescheduled in irqexit. > > This is only necessary under !preempt_model_preemptible() for which > we reuse the same logic as irqentry_exit_code_resched(). > > Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx> > --- > kernel/entry/common.c | 8 ++++++++ > kernel/sched/core.c | 36 +++++++++++++++++++++--------------- > 2 files changed, 29 insertions(+), 15 deletions(-) > > diff --git a/kernel/entry/common.c b/kernel/entry/common.c > index be61332c66b5..f1005595ebe7 100644 > --- a/kernel/entry/common.c > +++ b/kernel/entry/common.c > @@ -390,6 +390,9 @@ void raw_irqentry_exit_cond_resched(void) > preempt_schedule_irq(); > } > } > + > +void irqentry_exit_allow_resched(void) __alias(raw_irqentry_exit_cond_resched); Because typing raw_irqentry_exit_cond_resched() was too much effort? > + > #ifdef CONFIG_PREEMPT_DYNAMIC > #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) > DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched); > @@ -431,6 +434,11 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state) > instrumentation_begin(); > if (IS_ENABLED(CONFIG_PREEMPTION)) > irqentry_exit_cond_resched(); > + /* > + * We care about this clause only in the dynamic !preemptible case. > + */ > + if (unlikely(!preempt_model_preemptible() && resched_allowed())) > + irqentry_exit_allow_resched(); This is wrong, if we have dynamic preemption then we have CONFIG_PREEMPTION and we'll have that irqentry_exit_cond_resched() call. Basically what you've written above is something like: static_call(foo); // raw_foo() when A, NOP if !A if (!A) raw_foo(); And yeah, you've got the extra resched_allowed() thing in there, but that doesn't make it any better -- this is all quite horrible. What you really care about is the CONFIG_PREEMPTION=n case, but that you don't actually handle. > /* Covers both tracing and lockdep */ > trace_hardirqs_on(); > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 0d18c3969f90..11845a91b691 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -8597,28 +8599,32 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write); > * SC:preempt_schedule > * SC:preempt_schedule_notrace > * SC:irqentry_exit_cond_resched > + * SC:irqentry_exit_allow_resched > * > * > * NONE: > - * cond_resched <- __cond_resched > - * might_resched <- RET0 > - * preempt_schedule <- NOP > - * preempt_schedule_notrace <- NOP > - * irqentry_exit_cond_resched <- NOP > + * cond_resched <- __cond_resched > + * might_resched <- RET0 > + * preempt_schedule <- NOP > + * preempt_schedule_notrace <- NOP > + * irqentry_exit_cond_resched <- NOP > + * irqentry_exit_allow_resched <- irqentry_exit_allow_resched > * > * VOLUNTARY: > - * cond_resched <- __cond_resched > - * might_resched <- __cond_resched > - * preempt_schedule <- NOP > - * preempt_schedule_notrace <- NOP > - * irqentry_exit_cond_resched <- NOP > + * cond_resched <- __cond_resched > + * might_resched <- __cond_resched > + * preempt_schedule <- NOP > + * preempt_schedule_notrace <- NOP > + * irqentry_exit_cond_resched <- NOP > + * irqentry_exit_allow_resched <- irqentry_exit_allow_resched > * > * FULL: > - * cond_resched <- RET0 > - * might_resched <- RET0 > - * preempt_schedule <- preempt_schedule > - * preempt_schedule_notrace <- preempt_schedule_notrace > - * irqentry_exit_cond_resched <- irqentry_exit_cond_resched > + * cond_resched <- RET0 > + * might_resched <- RET0 > + * preempt_schedule <- preempt_schedule > + * preempt_schedule_notrace <- preempt_schedule_notrace > + * irqentry_exit_cond_resched <- irqentry_exit_cond_resched > + * irqentry_exit_allow_resched <- NOP > */ This ^ is all complete nonsense.. irqentry_exit_allow_resched() is not a static call. It's an alias of raw_irqentry_exit_cond_resched which circumvents the static call entirely.
