The scheduling policy for TIF_NEED_RESCHED_LAZY is to run to completion. Scheduling in exit_to_user_mode_loop() satisfies that. Scheduling while exiting to userspace, also guarantees that the task being scheduled away is entirely clear of any kernel encumbrances that cannot span across preemption. Ordinarily we don't need this extra protection: the preempt_count check is always available. However, cases where preempt_count might not be wholly dependable (ARCH_NO_PREEMPT configurations) will make use of this. Originally-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx> --- include/linux/entry-common.h | 2 +- kernel/entry/common.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index fb2e349a17d2..7a56440442df 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -59,7 +59,7 @@ #define EXIT_TO_USER_MODE_WORK \ (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \ _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \ - ARCH_EXIT_TO_USER_MODE_WORK) + _TIF_NEED_RESCHED_LAZY | ARCH_EXIT_TO_USER_MODE_WORK) /** * arch_enter_from_user_mode - Architecture specific sanity check for user mode regs diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 194c349b8be7..0d055c39690b 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -154,7 +154,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, local_irq_enable_exit_to_user(ti_work); - if (ti_work & _TIF_NEED_RESCHED) + if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) schedule(); if (ti_work & _TIF_UPROBE) -- 2.31.1
