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 [email protected] http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
