* Andi Kleen <[email protected]> wrote:
> Index: linux-2.6.15/lib/spinlock_debug.c
> ===================================================================
> --- linux-2.6.15.orig/lib/spinlock_debug.c
> +++ linux-2.6.15/lib/spinlock_debug.c
> @@ -68,13 +68,13 @@ static inline void debug_spin_unlock(spi
> static void __spin_lock_debug(spinlock_t *lock)
> {
> int print_once = 1;
> - u64 i;
>
> for (;;) {
> - for (i = 0; i < loops_per_jiffy * HZ; i++) {
> - cpu_relax();
> + unsigned long timeout = jiffies + HZ;
> + while (time_before(jiffies, timeout)) {
> if (__raw_spin_trylock(&lock->raw_lock))
> return;
> + cpu_relax();
The reason i added a loop counter was to solve the case where we are
spinning with interrupts disabled - jiffies wont increase there! But i
agree that loops_per_jiffy is the wrong metric to use.
a better solution would be to call __delay(1) after the first failed
attempt, that would make the delay at least 1 second long. It seems
__delay() is de-facto exported by every architecture, so we can rely on
it in the global spinlock code.
So how about the patch below instead?
[detail: i moved the __delay() after the second attempted trylock, this
way we'll have 2 trylocks without a delay - for ultra-short critical
sections.]
Ingo
----
fix spinlock debugging delays to not time out too early.
Bug found by Andi Kleen.
Signed-off-by: Ingo Molnar <[email protected]>
--- linux/lib/spinlock_debug.c.orig
+++ linux/lib/spinlock_debug.c
@@ -72,9 +72,9 @@ static void __spin_lock_debug(spinlock_t
for (;;) {
for (i = 0; i < loops_per_jiffy * HZ; i++) {
- cpu_relax();
if (__raw_spin_trylock(&lock->raw_lock))
return;
+ __delay(1);
}
/* lockup suspected: */
if (print_once) {
@@ -144,9 +144,9 @@ static void __read_lock_debug(rwlock_t *
for (;;) {
for (i = 0; i < loops_per_jiffy * HZ; i++) {
- cpu_relax();
if (__raw_read_trylock(&lock->raw_lock))
return;
+ __delay(1);
}
/* lockup suspected: */
if (print_once) {
@@ -217,9 +217,9 @@ static void __write_lock_debug(rwlock_t
for (;;) {
for (i = 0; i < loops_per_jiffy * HZ; i++) {
- cpu_relax();
if (__raw_write_trylock(&lock->raw_lock))
return;
+ __delay(1);
}
/* lockup suspected: */
if (print_once) {
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
