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

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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: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon 2020-06-30 14:06:04 +01:00
parent 364a5a8ae8
commit 5af76fb422
1 changed files with 4 additions and 3 deletions
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7
arch/arm64/kernel/alternative.c
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@ -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;