diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2025-12-15 17:52:31 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-01-22 11:11:19 +0100 |
| commit | 3c78aaec19b0621bf952756670c8b066a55202fe (patch) | |
| tree | 9b9a57025476627d16644a6bf4eebc559728d1f5 /kernel/entry/common.c | |
| parent | dfb630f548a7c715efb0651c6abf334dca75cd52 (diff) | |
entry: Hook up rseq time slice extension
Wire the grant decision function up in exit_to_user_mode_loop()
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251215155709.258157362@linutronix.de
Diffstat (limited to 'kernel/entry/common.c')
| -rw-r--r-- | kernel/entry/common.c | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 5c792b30c58a..9ef63e414791 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -17,6 +17,27 @@ void __weak arch_do_signal_or_restart(struct pt_regs *regs) { } #define EXIT_TO_USER_MODE_WORK_LOOP (EXIT_TO_USER_MODE_WORK) #endif +/* TIF bits, which prevent a time slice extension. */ +#ifdef CONFIG_PREEMPT_RT +/* + * Since rseq slice ext has a direct correlation to the worst case + * scheduling latency (schedule is delayed after all), only have it affect + * LAZY reschedules on PREEMPT_RT for now. + * + * However, since this delay is only applicable to userspace, a value + * for rseq_slice_extension_nsec that is strictly less than the worst case + * kernel space preempt_disable() region, should mean the scheduling latency + * is not affected, even for !LAZY. + * + * However, since this value depends on the hardware at hand, it cannot be + * pre-determined in any sensible way. Hence punt on this problem for now. + */ +# define TIF_SLICE_EXT_SCHED (_TIF_NEED_RESCHED_LAZY) +#else +# define TIF_SLICE_EXT_SCHED (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY) +#endif +#define TIF_SLICE_EXT_DENY (EXIT_TO_USER_MODE_WORK & ~TIF_SLICE_EXT_SCHED) + static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *regs, unsigned long ti_work) { @@ -28,8 +49,10 @@ static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *re local_irq_enable_exit_to_user(ti_work); - if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) - schedule(); + if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) { + if (!rseq_grant_slice_extension(ti_work & TIF_SLICE_EXT_DENY)) + schedule(); + } if (ti_work & _TIF_UPROBE) uprobe_notify_resume(regs); |