Commit 780de406 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

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



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: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201217134731.488135-5-npiggin@gmail.com
parent 54bb5033

arch/powerpc/mm/book3s64/radix_tlb.c

+6 −10
Original line number Diff line number Diff line
@@ -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: