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Subject[RFC PATCH 3/3] sched/Documentation: Point out use of preempt_schedule_irq()
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 <>
Cc: Jonathan Corbet <>
Cc: Ingo Molnar <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Cc: Julien Thierry <>
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
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