On Wed, Nov 30, 2022 at 10:44:55AM -0800, Paul E. McKenney wrote: > On Wed, Nov 30, 2022 at 01:56:17PM +0100, Uladzislau Rezki wrote: > > On Tue, Nov 29, 2022 at 03:38:33PM -0800, Paul E. McKenney wrote: > > > On Tue, Nov 29, 2022 at 04:58:21PM +0100, Uladzislau Rezki (Sony) wrote: > > > > Currently a need_offload_krc() function requires the krcp->lock > > > > to be held because krcp->head can not be checked concurrently. > > > > > > > > Fix it by updating the krcp->head using WRITE_ONCE() macro so > > > > it becomes lock-free and safe for readers to see a valid data > > > > without any locking. > > > > > > Don't we also need to use READ_ONCE() for the code loading this krcp->head > > > pointer? Or do the remaining plain C-language accesses somehow avoid > > > running concurrently with those new WRITE_ONCE() invocations? > > > > > It can be concurrent. I was thinking about it. For some reason i decided > > to keep readers as a "regular" ones for loading the krcp->head. > > > > In this case it might take time for readers to see an updated value > > as a worst case scenario. > > > > So i need to update it or upload one more patch on top of v2. Should > > i upload a new patch? > > Sending an additional patch should be fine. Unless you would rather it > be folded into one of the existing patches, in which case please start > with the set that I have queued. > Done. -- Uladzislau Rezki
