Commit 5af76fb4 authored by Will Deacon's avatar Will Deacon
Browse files

arm64: alternatives: Remove READ_ONCE() usage during patch operation 



In preparation for patching the internals of READ_ONCE() itself, replace
its usage on the alternatives patching patch with a volatile variable
instead.

Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 364a5a8a

arch/arm64/kernel/alternative.c

+4 −3
Original line number Diff line number Diff line
@@ -21,7 +21,8 @@ 
#define ALT_ORIG_PTR(a)		__ALT_PTR(a, orig_offset)

#define ALT_REPL_PTR(a)		__ALT_PTR(a, alt_offset)



static int all_alternatives_applied;

/* Volatile, as we may be patching the guts of READ_ONCE() */

static volatile int all_alternatives_applied;



static DECLARE_BITMAP(applied_alternatives, ARM64_NCAPS);
@@ -205,7 +206,7 @@ static int __apply_alternatives_multi_stop(void *unused) 


	/* We always have a CPU 0 at this point (__init) */

	if (smp_processor_id()) {

		while (!READ_ONCE(all_alternatives_applied))

		while (!all_alternatives_applied)

			cpu_relax();

		isb();

	} else {
@@ -217,7 +218,7 @@ static int __apply_alternatives_multi_stop(void *unused) 
		BUG_ON(all_alternatives_applied);

		__apply_alternatives(&region, false, remaining_capabilities);

		/* Barriers provided by the cache flushing */

		WRITE_ONCE(all_alternatives_applied, 1);

		all_alternatives_applied = 1;

	}



	return 0;