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Valentin Schneidermpe
Valentin Schneider
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mpe
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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 f1a0a37 ("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: f1a0a37 ("sched/core: Initialize the idle task with preemption disabled") Reported-by: Bharata B Rao <[email protected]> Signed-off-by: Valentin Schneider <[email protected]> Tested-by: Guenter Roeck <[email protected]> Tested-by: Bharata B Rao <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> Link: https://lore.kernel.org/r/[email protected]
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‎arch/powerpc/platforms/cell/smp.c‎

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@@ -78,9 +78,6 @@ static inline int smp_startup_cpu(unsigned int lcpu)
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pcpu = get_hard_smp_processor_id(lcpu);
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/* Fixup atomic count: it exited inside IRQ handler. */
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task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count = 0;
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/*
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* If the RTAS start-cpu token does not exist then presume the
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* cpu is already spinning.

‎arch/powerpc/platforms/pseries/smp.c‎

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@@ -105,9 +105,6 @@ static inline int smp_startup_cpu(unsigned int lcpu)
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return 1;
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}
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/* Fixup atomic count: it exited inside IRQ handler. */
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task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count = 0;
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/*
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* If the RTAS start-cpu token does not exist then presume the
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* cpu is already spinning.

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