From: Valentin Schneider <valentin.schneider@arm.com> stable inclusion from stable-5.10.50 commit bdf4d33e8342b90386156204e1da0cdfdb4bf146 bugzilla: 174522 https://gitee.com/openeuler/kernel/issues/I4DNFY Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 2c669ef6979c370f98d4b876e54f19613c81e075 upstream. 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 <bharata@linux.ibm.com> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Guenter Roeck <linux@roeck-us.net> Tested-by: Bharata B Rao <bharata@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210707183831.2106509-1-valentin.schneider@arm.co... Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Chen Jun <chenjun102@huawei.com> Acked-by: Weilong Chen <chenweilong@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.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 92922491a81c..624e80b00eb1 100644 --- a/arch/powerpc/platforms/pseries/smp.c +++ b/arch/powerpc/platforms/pseries/smp.c @@ -104,9 +104,6 @@ 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. -- 2.20.1