Since there are a few archs out there that call preempt_schedule_irq() within a need_resched() loop, point out that it's not needed. Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Julien Thierry <julien.thierry@xxxxxxx> Cc: linux-doc@xxxxxxxxxxxxxxx --- Documentation/scheduler/sched-arch.txt | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Documentation/scheduler/sched-arch.txt b/Documentation/scheduler/sched-arch.txt index a2f27bbf2cba..ae41a94da700 100644 --- a/Documentation/scheduler/sched-arch.txt +++ b/Documentation/scheduler/sched-arch.txt @@ -59,6 +59,16 @@ Your cpu_idle routines need to obey the following rules: arch/x86/kernel/process.c has examples of both polling and sleeping idle functions. +Kernel preemption +================= +When returning from interrupt context, you should call either of +preempt_schedule() or preempt_schedule_irq() if preemption is enabled +and need_resched() is true. + +Note that, unlike preempt_schedule(), preempt_schedule_irq() handles the +enabling and disabling of IRQs. Since it also loops on need_resched(), +you don't need to have that loop in your arch code. See +arch/arm64/kernel/entry.S for an example. Possible arch/ problems ======================= -- 2.20.1
