Hi Richard, thanks a million for your check-in! It indeed fixed our issues with TSan!
Best regards, Jan On Wed, Jan 9, 2019 at 3:55 PM Richard Hipp <d...@sqlite.org> wrote: > Check-in https://www.sqlite.org/src/info/383437be276719ac will perhaps > silence the harmless false-positives reported by TSAN. Please let us > know if it does not solve the problem for you. > > On 1/7/19, Jan Krčál <jkr...@google.com> wrote: > > Hi, > > > > as a Chrome developer, I've run into a data race flagged by > ThreadSanitizer > > in pcache1.c: > > > > When two threads write to in-memory sqlite DBs (each to its own separate > > DB), each thread has its own PCache1 with bPurgeable being false. Thus, > in > > both threads, pCache->pnPurgeable points to the static > > variable dummyCurrentPage. > > > > Even if bPurgeable is false, pCache->pnPurgeable gets incremented by > > pcache1AllocPage() and decremented by pcache1FreePage(). When each > pCache > > belongs to a different pGroup, the writes can happen concurrently on > those > > two threads and are not protected by any mutex. This results in a data > race > > that makes ThreadSanitizer unhappy. > > > > These writes are not needed in the first place because the value of > > pCache->pnPurgeable is never read if bPurgeable is false. Because the > value > > is never read, I can hardly imagine a situation this data race could lead > > to a real problem. Still, it is technically a data race with undefined > > behavior. Most importantly, I'd like ThreadSanitizer be happy with this > > code in this context. > > > > This is the first time I look into sqlite source code, does the text > above > > make sense to you? :) > > If so, the fix should be pretty simple. Can you please look into this or > > should I provide a patch? > > > > Best regards, > > Jan > > _______________________________________________ > > sqlite-users mailing list > > sqlite-users@mailinglists.sqlite.org > > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > > > > > -- > D. Richard Hipp > d...@sqlite.org > _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
