diff options
author | Peter Zijlstra <peterz@infradead.org> | 2013-08-14 14:55:46 +0200 |
---|---|---|
committer | Robin Randhawa <robin.randhawa@arm.com> | 2015-04-09 12:25:51 +0100 |
commit | 4ce0c44a90faff2bd4abff697bde1331626f3460 (patch) | |
tree | 0b8d9f8055904fdf7cb466ee6c00b1c6fedfcc06 /include | |
parent | bcfd221b8ba48122a4abcf85522f398ea35dc11e (diff) |
sched: Create more preempt_count accessors
We need a few special preempt_count accessors:
- task_preempt_count() for when we're interested in the preemption
count of another (non-running) task.
- init_task_preempt_count() for properly initializing the preemption
count.
- init_idle_preempt_count() a special case of the above for the idle
threads.
With these no generic code ever touches thread_info::preempt_count
anymore and architectures could choose to remove it.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 01028747559ac6c6f642a7bbd2875cc4f66b2feb)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
Conflicts:
include/asm-generic/preempt.h
Diffstat (limited to 'include')
-rw-r--r-- | include/asm-generic/preempt.h | 68 | ||||
-rw-r--r-- | include/trace/events/sched.h | 2 |
2 files changed, 69 insertions, 1 deletions
diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h new file mode 100644 index 000000000000..8100b1ec1715 --- /dev/null +++ b/include/asm-generic/preempt.h @@ -0,0 +1,68 @@ +#ifndef __ASM_PREEMPT_H +#define __ASM_PREEMPT_H + +#include <linux/thread_info.h> + +/* + * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users + * that think a non-zero value indicates we cannot preempt. + */ +static __always_inline int preempt_count(void) +{ + return current_thread_info()->preempt_count & ~PREEMPT_NEED_RESCHED; +} + +static __always_inline int *preempt_count_ptr(void) +{ + return ¤t_thread_info()->preempt_count; +} + +/* + * We now loose PREEMPT_NEED_RESCHED and cause an extra reschedule; however the + * alternative is loosing a reschedule. Better schedule too often -- also this + * should be a very rare operation. + */ +static __always_inline void preempt_count_set(int pc) +{ + *preempt_count_ptr() = pc; +} + +/* + * must be macros to avoid header recursion hell + */ +#define task_preempt_count(p) \ + (task_thread_info(p)->preempt_count & ~PREEMPT_NEED_RESCHED) + +#define init_task_preempt_count(p) do { \ + task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \ +} while (0) + +#define init_idle_preempt_count(p, cpu) do { \ + task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \ +} while (0) + +/* + * We fold the NEED_RESCHED bit into the preempt count such that + * preempt_enable() can decrement and test for needing to reschedule with a + * single instruction. + * + * We invert the actual bit, so that when the decrement hits 0 we know we both + * need to resched (the bit is cleared) and can resched (no preempt count). + */ + +static __always_inline void set_preempt_need_resched(void) +{ + *preempt_count_ptr() &= ~PREEMPT_NEED_RESCHED; +} + +static __always_inline void clear_preempt_need_resched(void) +{ + *preempt_count_ptr() |= PREEMPT_NEED_RESCHED; +} + +static __always_inline bool test_preempt_need_resched(void) +{ + return !(*preempt_count_ptr() & PREEMPT_NEED_RESCHED); +} + +#endif /* __ASM_PREEMPT_H */ diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h index e5586caff67a..2dee4ae666b6 100644 --- a/include/trace/events/sched.h +++ b/include/trace/events/sched.h @@ -103,7 +103,7 @@ static inline long __trace_sched_switch_state(struct task_struct *p) /* * For all intents and purposes a preempted task is a running task. */ - if (task_thread_info(p)->preempt_count & PREEMPT_ACTIVE) + if (task_preempt_count(p) & PREEMPT_ACTIVE) state = TASK_RUNNING | TASK_STATE_MAX; #endif |