path: root/cgit.c
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authorJohn Keeping <john@keeping.me.uk>2015-03-03 19:22:31 +0000
committerJason A. Donenfeld <Jason@zx2c4.com>2015-03-03 23:55:27 +0100
commitdb9a70b159a107da29f88865d63ba14dd127556f (patch)
tree8dd6c73a41bb49206c6bd2c4f1bbee08f295a6bf /cgit.c
parentMake root handling sane again. (diff)
cache: use F_SETLK to avoid stale lock files
If CGit is killed while it holds a lock on a cache slot (for example because it is taking too long to generate a page), the lock file will be left in place. This prevents any future attempt to use the same slot since it will fail to exclusively create the lock file. Since CGit is the only program that should be manipulating lock files, we can use advisory locking to detect whether another process is actually using the lock file or if it is now stale. I have confirmed that this works on Linux by setting a short TTL in a custom cgitrc and running the following with CGit patched to print a message to stderr if the fcntl(2) fails: $ export CGIT_CONFIG=$PWD/cgitrc $ export QUERY_STRING=url=cgit/tree/ui-shared.c $ ./cgit | grep -v -e '^<div class=.footer.>' \ -e '^Last-Modified: ' \ -e ^'Expires: ' >expect $ seq 50000 | dd bs=8192 | parallel -j200 "diff -u expect <(./cgit | grep -v -e '^<div class=.footer.>' \ -e '^Last-Modified: ' \ -e ^'Expires: ') || echo BAD" This printed the fail message several times without ever printing "BAD". Signed-off-by: John Keeping <john@keeping.me.uk>
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