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lib/vsprintf: Use acquire/release for ptr_key publication

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Replace the smp_wmb() + WRITE_ONCE() and READ_ONCE() + smp_rmb() barrier
pair with smp_store_release()/smp_load_acquire() on filled_random_ptr_key.

This expresses the publish/subscribe pattern more clearly and allows
architectures with native acquire/release instructions (e.g. arm64's
STLR/LDAR) to avoid the cost of full one-way barriers (DMB ISHST/ISHLD).

No functional change intended.

Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Assisted-by: DeepSeek:DeepSeek-V3
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20260902074805.398540-3-ruanjinjie@huawei.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
Jinjie Ruan 2026-09-02 15:47:59 +08:00 committed by Petr Mladek
parent 77ae27fd98
commit 72d907f23e
1 changed files with 4 additions and 7 deletions
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11
lib/vsprintf.c
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@ -762,9 +762,8 @@ static int fill_ptr_key(struct notifier_block *nb, unsigned long action, void *d
{
get_random_bytes(&ptr_key, sizeof(ptr_key));
/* Pairs with smp_rmb() before reading ptr_key. */
smp_wmb();
WRITE_ONCE(filled_random_ptr_key, true);
/* Pairs with smp_load_acquire() before reading ptr_key. */
smp_store_release(&filled_random_ptr_key, true);
return NOTIFY_DONE;
}
@ -781,12 +780,10 @@ static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
{
unsigned long hashval;
if (!READ_ONCE(filled_random_ptr_key))
/* Pairs with smp_store_release() after writing ptr_key. */
if (!smp_load_acquire(&filled_random_ptr_key))
return -EBUSY;
/* Pairs with smp_wmb() after writing ptr_key. */
smp_rmb();
#ifdef CONFIG_64BIT
hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);
/*