[PATCH v13 11/15] sched: add need-resched timed wait interface
From: Ankur Arora <hidden>
Date: 2026-07-02 01:35:16
Also in:
bpf, linux-arch, linux-pm, lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
Add tif_bitset_relaxed_wait() (and tif_need_resched_relaxed_wait() which wraps it) which takes the thread_info bit and timeout duration as parameters and waits until the bit is set or for the expiration of the timeout. The wait is implemented via smp_cond_load_relaxed_timeout(). smp_cond_load_relaxed_timeout() essentially provides the pattern used in poll_idle() where we spin in a loop waiting for the flag to change until a timeout occurs. tif_need_resched_relaxed_wait() allows us to abstract out the internals of waiting, scheduler specific details etc. Placed in linux/sched/idle.h instead of linux/thread_info.h to work around recursive include hell. Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rafael J. Wysocki <rafael@kernel.org> Cc: Daniel Lezcano <redacted> Cc: linux-pm@vger.kernel.org Signed-off-by: Ankur Arora <redacted> --- include/linux/sched/idle.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)
diff --git a/include/linux/sched/idle.h b/include/linux/sched/idle.h
index 8465ff1f20d1..ddee9b019895 100644
--- a/include/linux/sched/idle.h
+++ b/include/linux/sched/idle.h@@ -3,6 +3,7 @@ #define _LINUX_SCHED_IDLE_H #include <linux/sched.h> +#include <linux/sched/clock.h> enum cpu_idle_type { __CPU_NOT_IDLE = 0,
@@ -113,4 +114,32 @@ static __always_inline void current_clr_polling(void) } #endif +/* + * Caller needs to make sure that the thread context cannot be preempted + * or migrated, so current_thread_info() cannot change from under us. + * + * This also allows us to safely stay in the local_clock domain. + */ +static __always_inline bool tif_bitset_relaxed_wait(int tif, u64 timeout_ns) +{ + unsigned long flags; + + flags = smp_cond_load_relaxed_timeout(¤t_thread_info()->flags, + (VAL & BIT(tif)), + local_clock_noinstr(), + timeout_ns); + return flags & BIT(tif); +} + +/** + * tif_need_resched_relaxed_wait() - Wait for need-resched being set + * with no ordering guarantees until a timeout expires. + * + * @timeout_ns: timeout value. + */ +static __always_inline bool tif_need_resched_relaxed_wait(u64 timeout_ns) +{ + return tif_bitset_relaxed_wait(TIF_NEED_RESCHED, timeout_ns); +} + #endif /* _LINUX_SCHED_IDLE_H */
--
2.43.7