On 06/06/2012 10:24 AM, Peter Zijlstra wrote: > On Wed, 2012-06-06 at 09:18 -0700, tip-bot for Shai Fultheim wrote: > >> [ I absolutely hate these locking patterns ... yet I have no better idea. Maybe the gents on Cc: ... ] >> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > > Oh yuck, this is vile.. > > static struct static_key scale_mp_trainwreck = STATIC_KEY_INIT_FALSE; > > static DEFINE_SPINLOCK(_cpa_lock); > > static inline void cpa_lock(void) > { > if (static_key_false(&scale_mp_trainwreck)) > return; > > spin_lock(&_cpa_lock); > } > > static inline void cpa_unlock(void) > { > if (static_key_false(&scale_mp_trainwreck)) > return; > > spin_lock(&_cpa_lock); > } > > And then use cpa_{,un}lock(), and the scale-mp guys can > static_key_slow_inc(&scale_mp_trainwreck). > Actually, for this particular subcase I would use a synthetic CPUID bit and use static_cpu_has(). -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html