On 17:08, Neil Brown wrote: > > Do we really need to take the spin lock in the common case where > > conf->pending_bio_list.head is NULL? If not, the above could be > > optimized to the slightly faster and better readable > > > > struct bio *bio; > > > > if (!conf->pending_bio_list.head) > > return 0; > > spin_lock_irq(&conf->device_lock); > > bio = bio_list_get(&conf->pending_bio_list); > > ... > > spin_unlock_irq(&conf->device_lock); > > return 1; > > Maybe... If I write a memory location inside a spinlock, then after > the spinlock is dropped, I read that location on a different CPU, > am I always guaranteed to see the new value? or do I need some sort of > memory barrier? Are you worried about another CPU setting conf->pending_bio_list.head to != NULL after the if statement? If that's an issue I think also the original patch is problematic because the same might happen after the final spin_unlock_irq() but but before flush_pending_writes() returns zero. Andre -- The only person who always got his work done by Friday was Robinson Crusoe
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