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

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3c1853a9d1c0908f51713773917b2baaf66a11e2..bce63cbf23779b425db5aadf2522fb3f89c5ab1d 100644 (file)
--- 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);