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preempt/dynamic: Provide cond_resched() and might_resched() static calls 

Provide static calls to control cond_resched() (called in !CONFIG_PREEMPT)
and might_resched() (called in CONFIG_PREEMPT_VOLUNTARY) to that we
can override their behaviour when preempt= is overriden.

Since the default behaviour is full preemption, both their calls are
ignored when preempt= isn't passed.

  [fweisbec: branch might_resched() directly to __cond_resched(), only
             define static calls when PREEMPT_DYNAMIC]

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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-6-frederic@kernel.org
This commit is contained in:
Peter Zijlstra (Intel) 2021-01-18 15:12:20 +01:00 committed by Ingo Molnar
parent 6ef869e064
commit b965f1ddb4
3 changed files with 56 additions and 10 deletions
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23
include/linux/kernel.h
View File

@ -15,7 +15,7 @@
#include <linux/typecheck.h>
#include <linux/printk.h>
#include <linux/build_bug.h>
#include <linux/static_call_types.h>
#include <asm/byteorder.h>
#include <uapi/linux/kernel.h>
@ -81,11 +81,26 @@ struct pt_regs;
struct user;
#ifdef CONFIG_PREEMPT_VOLUNTARY
extern int _cond_resched(void);
# define might_resched() _cond_resched()
extern int __cond_resched(void);
# define might_resched() __cond_resched()
#elif defined(CONFIG_PREEMPT_DYNAMIC)
extern int __cond_resched(void);
DECLARE_STATIC_CALL(might_resched, __cond_resched);
static __always_inline void might_resched(void)
{
static_call(might_resched)();
}
#else
# define might_resched() do { } while (0)
#endif
#endif /* CONFIG_PREEMPT_* */
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
extern void ___might_sleep(const char *file, int line, int preempt_offset);

27
include/linux/sched.h
View File

@ -1871,11 +1871,32 @@ static inline int test_tsk_need_resched(struct task_struct *tsk)
* value indicates whether a reschedule was done in fact.
* cond_resched_lock() will drop the spinlock before scheduling,
*/
#ifndef CONFIG_PREEMPTION
extern int _cond_resched(void);
#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
extern int __cond_resched(void);
#ifdef CONFIG_PREEMPT_DYNAMIC
DECLARE_STATIC_CALL(cond_resched, __cond_resched);
static __always_inline int _cond_resched(void)
{
return static_call(cond_resched)();
}
#else
static inline int _cond_resched(void)
{
return __cond_resched();
}
#endif /* CONFIG_PREEMPT_DYNAMIC */
#else
static inline int _cond_resched(void) { return 0; }
#endif
#endif /* !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) */
#define cond_resched() ({ \
___might_sleep(__FILE__, __LINE__, 0); \

16
kernel/sched/core.c
View File

@ -6785,17 +6785,27 @@ SYSCALL_DEFINE0(sched_yield)
return 0;
}
#ifndef CONFIG_PREEMPTION
int __sched _cond_resched(void)
#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
int __sched __cond_resched(void)
{
if (should_resched(0)) {
preempt_schedule_common();
return 1;
}
#ifndef CONFIG_PREEMPT_RCU
rcu_all_qs();
#endif
return 0;
}
EXPORT_SYMBOL(_cond_resched);
EXPORT_SYMBOL(__cond_resched);
#endif
#ifdef CONFIG_PREEMPT_DYNAMIC
DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
EXPORT_STATIC_CALL(cond_resched);
DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
EXPORT_STATIC_CALL(might_resched);
#endif
/*