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lib/vsprintf: Remove static_branch_likely() from __ptr_to_hashval().

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Using static_branch_likely() to signal that ptr_key has been filled is a
bit much given that it is not a fast path.

Replace static_branch_likely() with bool for condition and a memory
barrier for ptr_key.

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220927104912.622645-2-bigeasy@linutronix.de
This commit is contained in:
Sebastian Andrzej Siewior 2022-09-27 12:49:11 +02:00 committed by Petr Mladek
parent a1b02751d6
commit e4279b5998
1 changed files with 8 additions and 11 deletions
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19
lib/vsprintf.c
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@ -750,12 +750,7 @@ static int __init debug_boot_weak_hash_enable(char *str)
}
early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
static DEFINE_STATIC_KEY_FALSE(filled_random_ptr_key);
static void enable_ptr_key_workfn(struct work_struct *work)
{
static_branch_enable(&filled_random_ptr_key);
}
static bool filled_random_ptr_key __read_mostly;
/* Maps a pointer to a 32 bit unique identifier. */
static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
@ -763,24 +758,26 @@ static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
static siphash_key_t ptr_key __read_mostly;
unsigned long hashval;
if (!static_branch_likely(&filled_random_ptr_key)) {
if (!READ_ONCE(filled_random_ptr_key)) {
static bool filled = false;
static DEFINE_SPINLOCK(filling);
static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
unsigned long flags;
if (!system_unbound_wq || !rng_is_initialized() ||
if (!rng_is_initialized() ||
!spin_trylock_irqsave(&filling, flags))
return -EAGAIN;
if (!filled) {
get_random_bytes(&ptr_key, sizeof(ptr_key));
queue_work(system_unbound_wq, &enable_ptr_key_work);
/* Pairs with smp_rmb() before reading ptr_key. */
smp_wmb();
WRITE_ONCE(filled_random_ptr_key, true);
filled = true;
}
spin_unlock_irqrestore(&filling, flags);
}
/* Pairs with smp_wmb() after writing ptr_key. */
smp_rmb();
#ifdef CONFIG_64BIT
hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);