schedule_user() was traditionally used by the entry code's tail to preempt userspace after the call to user_enter(). Indeed the call to user_enter() used to be performed upon syscall exit slow path which was right before the last opportunity to schedule() while resuming to userspace. The context tracking state had to be saved on the task stack and set back to CONTEXT_KERNEL temporarily in order to safely switch to another task.
Only a few archs use it now and those implementing HAVE_CONTEXT_TRACKING_OFFSTACK definetly can't rely on it. Signed-off-by: Frederic Weisbecker <frede...@kernel.org> Cc: Marcelo Tosatti <mtosa...@redhat.com> Cc: Paul E. McKenney <paul...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Phil Auld <pa...@redhat.com> Cc: Thomas Gleixner <t...@linutronix.de> --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d31a79e073e3..cb7afcfbb809 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4632,7 +4632,7 @@ void __sched schedule_idle(void) } while (need_resched()); } -#ifdef CONFIG_CONTEXT_TRACKING +#if defined(CONFIG_CONTEXT_TRACKING) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK) asmlinkage __visible void __sched schedule_user(void) { /* -- 2.25.1