On Wed, Apr 30, 2014 at 06:40:38PM -0400, Wang, Xiaoming wrote:
> loops_per_jiffy*Hz is not always 1 second exactly
> it depends on the realization of _delay() .
> delay_tsc is used as _delay() in arch/x86/lib/delay.c
> It makes loop loops_per_jiffy larger than exception
> and causes one thread can not obtain the spin lock for
> a long time which may trigger HARD LOCKUP in this case.
> So we use cpu_clock() which is more accurate.
>
> Signed-off-by: Chuansheng Liu <chuansheng....@intel.com>
> Signed-off-by: xiaoming wang <xiaoming.w...@intel.com>
> ---
> kernel/locking/spinlock_debug.c | 9 ++++++---
> 1 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c
> index 0374a59..471d26c 100644
> --- a/kernel/locking/spinlock_debug.c
> +++ b/kernel/locking/spinlock_debug.c
> @@ -105,10 +105,13 @@ static inline void debug_spin_unlock(raw_spinlock_t
> *lock)
>
> static void __spin_lock_debug(raw_spinlock_t *lock)
> {
> - u64 i;
> - u64 loops = loops_per_jiffy * HZ;
> + u64 t;
> + u64 one_second = 1000000000;
> + u32 this_cpu = raw_smp_processor_id();
> +
> + t = cpu_clock(this_cpu);
>
> - for (i = 0; i < loops; i++) {
> + while (cpu_clock(this_cpu) - t < one_second) {
> if (arch_spin_trylock(&lock->raw_lock))
> return;
> __delay(1);
Yep, and now you've broken support for archs that fall back to jiffies
for cpu_clock :-), jiffies need not progress if you've got IRQs
disabled.
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