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Subject[tip: sched/core] preempt/dynamic: Provide irqentry_exit_cond_resched() static call
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 74345075999752a7a9c805fe5e2ec770345cd1ca
Gitweb: https://git.kernel.org/tip/74345075999752a7a9c805fe5e2ec770345cd1ca
Author: Peter Zijlstra (Intel) <peterz@infradead.org>
AuthorDate: Mon, 18 Jan 2021 15:12:22 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 05 Feb 2021 17:19:57 +01:00

preempt/dynamic: Provide irqentry_exit_cond_resched() static call

Provide static call to control IRQ preemption (called in CONFIG_PREEMPT)
so that we can override its behaviour when preempt= is overriden.

Since the default behaviour is full preemption, its call is
initialized to provide IRQ preemption when preempt= isn't passed.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-8-frederic@kernel.org
---
include/linux/entry-common.h | 4 ++++
kernel/entry/common.c | 10 +++++++++-
2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index ca86a00..1401c93 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -2,6 +2,7 @@
#ifndef __LINUX_ENTRYCOMMON_H
#define __LINUX_ENTRYCOMMON_H

+#include <linux/static_call_types.h>
#include <linux/tracehook.h>
#include <linux/syscalls.h>
#include <linux/seccomp.h>
@@ -453,6 +454,9 @@ irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
* Conditional reschedule with additional sanity checks.
*/
void irqentry_exit_cond_resched(void);
+#ifdef CONFIG_PREEMPT_DYNAMIC
+DECLARE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+#endif

/**
* irqentry_exit - Handle return from exception that used irqentry_enter()
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 3783416..84fa7ec 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -393,6 +393,9 @@ void irqentry_exit_cond_resched(void)
preempt_schedule_irq();
}
}
+#ifdef CONFIG_PREEMPT_DYNAMIC
+DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+#endif

noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
{
@@ -419,8 +422,13 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
}

instrumentation_begin();
- if (IS_ENABLED(CONFIG_PREEMPTION))
+ if (IS_ENABLED(CONFIG_PREEMPTION)) {
+#ifdef CONFIG_PREEMT_DYNAMIC
+ static_call(irqentry_exit_cond_resched)();
+#else
irqentry_exit_cond_resched();
+#endif
+ }
/* Covers both tracing and lockdep */
trace_hardirqs_on();
instrumentation_end();
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