Valentin Schneider f1a0a376ca sched/core: Initialize the idle task with preemption disabled ... As pointed out by commit de9b8f5dcb ("sched: Fix crash trying to dequeue/enqueue the idle thread") init_idle() can and will be invoked more than once on the same idle task. At boot time, it is invoked for the boot CPU thread by sched_init(). Then smp_init() creates the threads for all the secondary CPUs and invokes init_idle() on them. As the hotplug machinery brings the secondaries to life, it will issue calls to idle_thread_get(), which itself invokes init_idle() yet again. In this case it's invoked twice more per secondary: at _cpu_up(), and at bringup_cpu(). Given smp_init() already initializes the idle tasks for all *possible* CPUs, no further initialization should be required. Now, removing init_idle() from idle_thread_get() exposes some interesting expectations with regards to the idle task's preempt_count: the secondary startup always issues a preempt_disable(), requiring some reset of the preempt count to 0 between hot-unplug and hotplug, which is currently served by idle_thread_get() -> idle_init(). Given the idle task is supposed to have preemption disabled once and never see it re-enabled, it seems that what we actually want is to initialize its preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove init_idle() from idle_thread_get(). Secondary startups were patched via coccinelle: @begone@ @@ -preempt_disable(); ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com		2021-05-12 13:01:45 +02:00
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abiv1	mm: move page_mapping_file to pagemap.h	2021-04-30 11:20:37 -07:00
abiv2	csky: Fixup compile error	2021-02-27 22:04:14 +08:00
boot	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
configs	csky: Minimize defconfig to support buildroot config.fragment	2020-02-21 15:43:25 +08:00
include	Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2021-05-02 09:14:01 -07:00
kernel	sched/core: Initialize the idle task with preemption disabled	2021-05-12 13:01:45 +02:00
lib	arch/csky patches for 5.13-rc1	2021-05-03 12:58:31 -07:00
mm	arch/csky patches for 5.13-rc1	2021-05-03 12:58:31 -07:00
Kconfig	csky: change a Kconfig symbol name to fix e1000 build error	2021-04-16 16:10:36 -07:00
Kconfig.debug	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
Kconfig.platforms	csky/Kconfig: Add Kconfig.platforms to support some drivers	2020-02-21 15:43:24 +08:00
Makefile	csky: Fixup calltrace panic	2020-05-13 17:55:06 +08:00