Idiocy in audit_serial()

Someone reported livelock on a 16-way itanic box, in audit_serial(). Looking at it, that doesn't really surprise me much. An audit.78 kernel is building with this... --- linux-2.6.9/kernel/audit.c~ 2005-06-30 17:45:22.000000000 +0100 +++ linux-2.6.9/kernel/audit.c 2005-07-15 08:45:38.000000000 +0100 @@ -678,26 +678,25 @@ err: * (timestamp,serial) tuple is unique for each syscall and is live from * syscall entry to syscall exit. * - * Atomic values are only guaranteed to be 24-bit, so we count down. - * * NOTE: Another possibility is to store the formatted records off the * audit context (for those records that have a context), and emit them * all at syscall exit. However, this could delay the reporting of * significant errors until syscall exit (or never, if the system * halts). */ + unsigned int audit_serial(void) { - static atomic_t serial = ATOMIC_INIT(0xffffff); - unsigned int a, b; + static spinlock_t serial_lock = SPIN_LOCK_UNLOCKED; + static unsigned int serial = 0; + + unsigned long flags; + unsigned int ret; - do { - a = atomic_read(&serial); - if (atomic_dec_and_test(&serial)) - atomic_set(&serial, 0xffffff); - b = atomic_read(&serial); - } while (b != a - 1); + spin_lock_irqsave(&serial_lock, flags); + ret = serial++; + spin_unlock_irqrestore(&serial_lock, flags); - return 0xffffff - b; + return ret; } static inline void audit_get_stamp(struct audit_context *ctx, -- dwmw2