| From 2c669ef6979c370f98d4b876e54f19613c81e075 Mon Sep 17 00:00:00 2001 |
| From: Valentin Schneider <valentin.schneider@arm.com> |
| Date: Wed, 7 Jul 2021 19:38:31 +0100 |
| Subject: powerpc/preempt: Don't touch the idle task's preempt_count during hotplug |
| |
| From: Valentin Schneider <valentin.schneider@arm.com> |
| |
| 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.com |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/powerpc/platforms/cell/smp.c | 3 --- |
| arch/powerpc/platforms/pseries/smp.c | 3 --- |
| 2 files changed, 6 deletions(-) |
| |
| --- a/arch/powerpc/platforms/cell/smp.c |
| +++ b/arch/powerpc/platforms/cell/smp.c |
| @@ -78,9 +78,6 @@ static inline int smp_startup_cpu(unsign |
| |
| 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. |
| --- a/arch/powerpc/platforms/pseries/smp.c |
| +++ b/arch/powerpc/platforms/pseries/smp.c |
| @@ -104,9 +104,6 @@ static inline int smp_startup_cpu(unsign |
| 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. |
