Messages in this thread | | | Date | Wed, 12 Aug 2009 09:43:32 +0400 | Subject | Re: [patch 4/4] ipc: sem optimise simple operations | From | Cyrill Gorcunov <> |
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On 8/12/09, Nick Piggin <npiggin@suse.de> wrote: > On Wed, Aug 12, 2009 at 12:07:11AM +0400, Cyrill Gorcunov wrote: >> [npiggin@suse.de - Tue, Aug 11, 2009 at 09:09:06PM +1000] >> ... >> | +static void update_queue_simple(struct sem_array *sma, ushort semnum) >> | +{ >> | + if (unlikely(sma->complex_count)) { >> | + update_queue(sma); >> | + } else { >> | + struct sem *sem; >> | + >> | + sem = &sma->sem_base[semnum]; >> | + if (sem->semval > 0) >> | + update_negv_queue(sma, sem); >> | + if (sem->semval == 0) >> | + update_zero_queue(sma, sem); >> | + } >> | +} >> | + >> ... >> >> Hi Nick, >> >> mostly probably miss something but can't we trgigger BUG_ON at updating >> zero queue if semaphore was created with undo list and via new operation >> reached -ERANGE on undo value? >> >> Again, I could be missing something or plain wrong. Just a thought. > > Hi Cyrill, > > Thanks for looking... Hmm, you mean BUG_ON(error) due to try_atomic_semop > returning -ERANGE? I think it should not be possible because it should > prevent any operation from bringing the undo list to -ERANGE so then any > operation which does not modify the sem value should not go out of range > I think. > > (I think it would be a bug if we ever return -ERANGE for a wait-for-zero > operation). > > Thanks, > Nick > Thanks for explanation, Nick! I meant exactly that.
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