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powerpc/64s/radix: Allow mm_cpumask trimming from external sources

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mm_cpumask trimming is currently restricted to be issued by the current
thread of a single-threaded mm. This patch relaxes that and allows the
mask to be trimmed from any context.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201217134731.488135-5-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin
2020-12-17 23:47:28 +10:00
committed by Michael Ellerman
parent 54bb503345
commit 780de40601
1 changed files with 6 additions and 10 deletions
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16
arch/powerpc/mm/book3s64/radix_tlb.c
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@@ -666,20 +666,16 @@ static void do_exit_flush_lazy_tlb(void *arg)
}
/*
* This IPI is only initiated from a CPU which is running mm which
* is a single-threaded process, so there will not be another racing
* IPI coming in where we would find our cpumask already clear.
*
* Nothing else clears our bit in the cpumask except CPU offlining,
* in which case we should not be taking IPIs here. However check
* this just in case the logic is wrong somewhere, and don't underflow
* the active_cpus count.
* This IPI may be initiated from any source including those not
* running the mm, so there may be a racing IPI that comes after
* this one which finds the cpumask already clear. Check and avoid
* underflowing the active_cpus count in that case. The race should
* not otherwise be a problem, but the TLB must be flushed because
* that's what the caller expects.
*/
if (cpumask_test_cpu(cpu, mm_cpumask(mm))) {
atomic_dec(&mm->context.active_cpus);
cpumask_clear_cpu(cpu, mm_cpumask(mm));
} else {
WARN_ON_ONCE(1);
}
out_flush: