From 2c669ef6979c370f98d4b876e54f19613c81e075 Mon Sep 17 00:00:00 2001 From: Valentin Schneider Date: Wed, 7 Jul 2021 19:38:31 +0100 Subject: [PATCH] powerpc/preempt: Don't touch the idle task's preempt_count during hotplug Powerpc currently resets a CPU's idle task preempt_count to 0 before said task starts executing the secondary startup routine (and becomes an idle task proper). This conflicts with commit f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled"). which initializes all of the idle tasks' preempt_count to PREEMPT_DISABLED during smp_init(). Note that this was superfluous before said commit, as back then the hotplug machinery would invoke init_idle() via idle_thread_get(), which would have already reset the CPU's idle task's preempt_count to PREEMPT_ENABLED. Get rid of this preempt_count write. Fixes: f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled") Reported-by: Bharata B Rao Signed-off-by: Valentin Schneider Tested-by: Guenter Roeck Tested-by: Bharata B Rao Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210707183831.2106509-1-valentin.schneider@arm.com --- arch/powerpc/platforms/cell/smp.c | 3 --- arch/powerpc/platforms/pseries/smp.c | 3 --- 2 files changed, 6 deletions(-) diff --git a/arch/powerpc/platforms/cell/smp.c b/arch/powerpc/platforms/cell/smp.c index c855a0aeb49c..d7ab868aab54 100644 --- a/arch/powerpc/platforms/cell/smp.c +++ b/arch/powerpc/platforms/cell/smp.c @@ -78,9 +78,6 @@ static inline int smp_startup_cpu(unsigned int lcpu) pcpu = get_hard_smp_processor_id(lcpu); - /* Fixup atomic count: it exited inside IRQ handler. */ - task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count = 0; - /* * If the RTAS start-cpu token does not exist then presume the * cpu is already spinning. diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c index 096629f54576..f47429323eee 100644 --- a/arch/powerpc/platforms/pseries/smp.c +++ b/arch/powerpc/platforms/pseries/smp.c @@ -105,9 +105,6 @@ static inline int smp_startup_cpu(unsigned int lcpu) return 1; } - /* Fixup atomic count: it exited inside IRQ handler. */ - task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count = 0; - /* * If the RTAS start-cpu token does not exist then presume the * cpu is already spinning. -- 2.39.5