Commit 04b8637b authored Aug 04, 2015 by Will Deacon

arm64: alternatives: ensure secondary CPUs execute ISB after patching



In order to guarantee that the patched instruction stream is visible to
a CPU, that CPU must execute an isb instruction after any related cache
maintenance has completed.

The instruction patching routines in kernel/insn.c get this right for
things like jump labels and ftrace, but the alternatives patching omits
it entirely leaving secondary cores in a potential limbo between the old
and the new code.

This patch adds an isb following the secondary polling loop in the
altenatives patching.

Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 7f08a414

arch/arm64/kernel/alternative.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -132,6 +132,7 @@ static int __apply_alternatives_multi_stop(void *unused)
		if (smp_processor_id()) {
		while (!READ_ONCE(patched))
		cpu_relax();
		isb();
		} else {
		BUG_ON(patched);
		__apply_alternatives(&region);

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