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| author |   Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2022-09-27 12:49:11 +0200 |
|---|---|---|
| committer |   Petr Mladek <pmladek@suse.com> | 2022-09-29 13:44:27 +0200 |
| commit | e4279b599863dd1aa71fb8e35bffa943545bbaeb (patch) | |
| tree | 396869d44ae7fc76f858f862f57eefd8a3daabd2 | |
| parent | Merge tag 'printk-for-5.20-sane' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux (diff) | |
| download | linux-dev-e4279b599863dd1aa71fb8e35bffa943545bbaeb.tar.xz linux-dev-e4279b599863dd1aa71fb8e35bffa943545bbaeb.zip | |
lib/vsprintf: Remove static_branch_likely() from __ptr_to_hashval().
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
| -rw-r--r-- | lib/vsprintf.c | 19 |
1 files changed, 8 insertions, 11 deletions
diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 3c1853a9d1c0..bce63cbf2377 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -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); |