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Date: Wed, 6 Apr 2022 19:48:10 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Dan Williams <dan.j.williams@...el.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
"Shankar, Ravi V" <ravi.v.shankar@...el.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH V9 01/45] entry: Create an internal
irqentry_exit_cond_resched() call
On Thu, Mar 10, 2022 at 09:19:35AM -0800, Ira wrote:
> From: Ira Weiny <ira.weiny@...el.com>
Rebasing to 5.18-rc1 revealed a different fix has been applied for this
work.[1]
Please disregard this patch.
Ira
[1] 4624a14f4daa ("sched/preempt: Simplify irqentry_exit_cond_resched()
callers")
>
> The static call to irqentry_exit_cond_resched() was not properly being
> overridden when called from xen_pv_evtchn_do_upcall().
>
> Define __irqentry_exit_cond_resched() as the static call and place the
> override logic in irqentry_exit_cond_resched().
>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
>
> ---
> Changes for V9
> Update the commit message a bit
>
> Because this was found via code inspection and it does not actually fix
> any seen bug I've not added a fixes tag.
>
> But for reference:
> Fixes: 40607ee97e4e ("preempt/dynamic: Provide irqentry_exit_cond_resched() static call")
> ---
> include/linux/entry-common.h | 5 ++++-
> kernel/entry/common.c | 23 +++++++++++++--------
> kernel/sched/core.c | 40 ++++++++++++++++++------------------
> 3 files changed, 38 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index 2e2b8d6140ed..ddaffc983e62 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -455,10 +455,13 @@ irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
> * Conditional reschedule with additional sanity checks.
> */
> void irqentry_exit_cond_resched(void);
> +
> +void __irqentry_exit_cond_resched(void);
> #ifdef CONFIG_PREEMPT_DYNAMIC
> -DECLARE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
> +DECLARE_STATIC_CALL(__irqentry_exit_cond_resched, __irqentry_exit_cond_resched);
> #endif
>
> +
> /**
> * irqentry_exit - Handle return from exception that used irqentry_enter()
> * @regs: Pointer to pt_regs (exception entry regs)
> diff --git a/kernel/entry/common.c b/kernel/entry/common.c
> index bad713684c2e..490442a48332 100644
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
> @@ -380,7 +380,7 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
> return ret;
> }
>
> -void irqentry_exit_cond_resched(void)
> +void __irqentry_exit_cond_resched(void)
> {
> if (!preempt_count()) {
> /* Sanity check RCU and thread stack */
> @@ -392,9 +392,20 @@ void irqentry_exit_cond_resched(void)
> }
> }
> #ifdef CONFIG_PREEMPT_DYNAMIC
> -DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
> +DEFINE_STATIC_CALL(__irqentry_exit_cond_resched, __irqentry_exit_cond_resched);
> #endif
>
> +void irqentry_exit_cond_resched(void)
> +{
> + if (IS_ENABLED(CONFIG_PREEMPTION)) {
> +#ifdef CONFIG_PREEMPT_DYNAMIC
> + static_call(__irqentry_exit_cond_resched)();
> +#else
> + __irqentry_exit_cond_resched();
> +#endif
> + }
> +}
> +
> noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
> {
> lockdep_assert_irqs_disabled();
> @@ -420,13 +431,7 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
> }
>
> instrumentation_begin();
> - if (IS_ENABLED(CONFIG_PREEMPTION)) {
> -#ifdef CONFIG_PREEMPT_DYNAMIC
> - static_call(irqentry_exit_cond_resched)();
> -#else
> - irqentry_exit_cond_resched();
> -#endif
> - }
> + irqentry_exit_cond_resched();
> /* Covers both tracing and lockdep */
> trace_hardirqs_on();
> instrumentation_end();
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 9745613d531c..f56db4bd9730 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6571,29 +6571,29 @@ EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
> * SC:might_resched
> * SC:preempt_schedule
> * SC:preempt_schedule_notrace
> - * SC:irqentry_exit_cond_resched
> + * SC:__irqentry_exit_cond_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
> *
> * 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
> *
> * 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
> */
>
> enum {
> @@ -6629,7 +6629,7 @@ void sched_dynamic_update(int mode)
> static_call_update(might_resched, __cond_resched);
> static_call_update(preempt_schedule, __preempt_schedule_func);
> static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
> - static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
> + static_call_update(__irqentry_exit_cond_resched, __irqentry_exit_cond_resched);
>
> switch (mode) {
> case preempt_dynamic_none:
> @@ -6637,7 +6637,7 @@ void sched_dynamic_update(int mode)
> static_call_update(might_resched, (void *)&__static_call_return0);
> static_call_update(preempt_schedule, NULL);
> static_call_update(preempt_schedule_notrace, NULL);
> - static_call_update(irqentry_exit_cond_resched, NULL);
> + static_call_update(__irqentry_exit_cond_resched, NULL);
> pr_info("Dynamic Preempt: none\n");
> break;
>
> @@ -6646,7 +6646,7 @@ void sched_dynamic_update(int mode)
> static_call_update(might_resched, __cond_resched);
> static_call_update(preempt_schedule, NULL);
> static_call_update(preempt_schedule_notrace, NULL);
> - static_call_update(irqentry_exit_cond_resched, NULL);
> + static_call_update(__irqentry_exit_cond_resched, NULL);
> pr_info("Dynamic Preempt: voluntary\n");
> break;
>
> @@ -6655,7 +6655,7 @@ void sched_dynamic_update(int mode)
> static_call_update(might_resched, (void *)&__static_call_return0);
> static_call_update(preempt_schedule, __preempt_schedule_func);
> static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
> - static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
> + static_call_update(__irqentry_exit_cond_resched, __irqentry_exit_cond_resched);
> pr_info("Dynamic Preempt: full\n");
> break;
> }
> --
> 2.35.1
>
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