Hugh Dickins <hughd@xxxxxxxxxx> writes: > On Tue, 3 Aug 2021, Matthew Wilcox wrote: >> On Tue, Aug 03, 2021 at 04:14:38PM +0800, Huang, Ying wrote: >> > Matthew Wilcox <willy@xxxxxxxxxxxxx> writes: >> > > But I REALLY REALLY REALLY want a reproducer. Right now, I have a hard >> > > time believing this, or any of the other races can really happen. >> > >> > I think the race is only theoretical too. Firstly, swapoff is a rare >> > operations in practice; secondly, the race window is really small. >> >> So do something to provoke it. Widen the window. Put an msleep(1000) >> between *pagep = NULL and the call to get_swap_device(). That's assuming >> that the swapon/swapoff loop that I proposed doesn't work. Did you >> try it? > > I've been doing that swapon/swapoff loop for years, while running kernel > builds on tmpfs going out to swap; for better or worse on baremetal not VM. > > You're right that few will ever need that level of reliability; but it > has caught problems from time to time, and I do insist on fixing them. > > I'm not as insistent as you on wanting a reproducer; and we all take pride > sometimes in fixing ever more inconceivable bugs. I'm not against that, > but it's easy to end up with a fix more dangerous than what it claims to > fix, rather like with random newbie cleanups. Yes. I totally agree, bug fixing is hard. Best Regards, Huang, Ying
