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authorMark Brown <broonie@kernel.org>2018-07-18 13:37:19 +0100
committerMark Brown <broonie@kernel.org>2018-07-18 13:37:19 +0100
commitfaf34726275b225a9954f2901364c053e6e3d1f0 (patch)
tree3ac169b40a37387cf986331b9371db8b0c5b7af7 /arch/arm64
parent77c2bedd8f1658a47e015e77ee1f86b619707735 (diff)
parentcff26c95b24c7b7147db17b623dee946bd25ec95 (diff)
Merge tag 'v4.14.56' into linux-linaro-lsk-v4.14
This is the 4.14.56 stable release
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/include/asm/simd.h19
1 files changed, 7 insertions, 12 deletions
diff --git a/arch/arm64/include/asm/simd.h b/arch/arm64/include/asm/simd.h
index fa8b3fe932e6..6495cc51246f 100644
--- a/arch/arm64/include/asm/simd.h
+++ b/arch/arm64/include/asm/simd.h
@@ -29,20 +29,15 @@ DECLARE_PER_CPU(bool, kernel_neon_busy);
static __must_check inline bool may_use_simd(void)
{
/*
- * The raw_cpu_read() is racy if called with preemption enabled.
- * This is not a bug: kernel_neon_busy is only set when
- * preemption is disabled, so we cannot migrate to another CPU
- * while it is set, nor can we migrate to a CPU where it is set.
- * So, if we find it clear on some CPU then we're guaranteed to
- * find it clear on any CPU we could migrate to.
- *
- * If we are in between kernel_neon_begin()...kernel_neon_end(),
- * the flag will be set, but preemption is also disabled, so we
- * can't migrate to another CPU and spuriously see it become
- * false.
+ * kernel_neon_busy is only set while preemption is disabled,
+ * and is clear whenever preemption is enabled. Since
+ * this_cpu_read() is atomic w.r.t. preemption, kernel_neon_busy
+ * cannot change under our feet -- if it's set we cannot be
+ * migrated, and if it's clear we cannot be migrated to a CPU
+ * where it is set.
*/
return !in_irq() && !irqs_disabled() && !in_nmi() &&
- !raw_cpu_read(kernel_neon_busy);
+ !this_cpu_read(kernel_neon_busy);
}
#else /* ! CONFIG_KERNEL_MODE_NEON */