From: Junio C Hamano Date: Fri, 30 Jun 2006 16:44:16 GMT Subject: Re: [PATCH 1/3] Add read_cache_from() and discard_cache() Message-ID: <7v3bdmk2zj.fsf@assigned-by-dhcp.cox.net> In-Reply-To: Johannes Schindelin writes: > +int discard_cache() > +{ > + int ret; > + > + if (cache_mmap == NULL) > + return 0; > + ret = munmap(cache_mmap, cache_mmap_size); > + cache_mmap = NULL; > + cache_mmap_size = 0; > + active_nr = active_cache_changed = 0; > + /* no need to throw away allocated active_cache */ > + return ret; > +} > + I haven't been following the details of the patches in this thread while they are being cooked actively, but two things to look out for are: - I am guessing you run discard_cache() because you want to read in a new cache (or start from a clean slate). I am not sure what you are doing with the old cache tree data structure. If you are starting from a clean slate (i.e. there is no read_cache_from() after you call discard_cache), you would probably need to discard the old cache tree; otherwise your next write-tree may produce an incorrect index file. If you keep the old one and later swap it in, the problem might be even more severe. - index_timestamp is left as the old value in this patch when you switch cache using read_cache_from() directly. I have a suspicion you may be bitten by "Racy Git" problem, especially because the operations are supposed to happen quickly thanks to the effort of you two ;-) increasing the risks that the file timestamp of the working tree file and the cached entry match.