On 11/30, Jeff King wrote: > On Wed, Nov 30, 2016 at 06:59:52PM -0500, Jeff King wrote: > > > So I think there is some other chdir(). I'm not sure if there is an easy > > way to get a backtrace on every call to chdir() in every thread. I'm > > sure somebody more clever than me could figure out how to make gdb do it > > automatically, but it might be workable manually. I think the chdir was > > in the main thread. > > Ah, that turned out to be quite easy. The culprit is probably: > > (gdb) bt > #0 chdir () at ../sysdeps/unix/syscall-template.S:84 > #1 0x00005555555fe259 in real_path_internal (path=0x5555559f6b30 "su:b/../.git/modules/su:b", die_on_error=1) > at abspath.c:84 > #2 0x00005555555fe48a in real_path (path=0x5555559f6b30 "su:b/../.git/modules/su:b") at abspath.c:135 > #3 0x00005555556d09e6 in read_gitfile_gently (path=0x5555559f6ac0 "su:b/.git", return_error_code=0x0) > at setup.c:555 > #4 0x00005555556d19cf in resolve_gitdir (suspect=0x5555559f6ac0 "su:b/.git") at setup.c:1021 > #5 0x00005555556e7e34 in is_submodule_populated (path=0x5555559f5ec8 "su:b") at submodule.c:244 > #6 0x00005555555a0f05 in grep_submodule (opt=0x7fffffffd8b0, sha1=0x0, filename=0x5555559f5ec8 "su:b", > path=0x5555559f5ec8 "su:b") at builtin/grep.c:619 > #7 0x00005555555a12ac in grep_cache (opt=0x7fffffffd8b0, pathspec=0x7fffffffd880, cached=0) at builtin/grep.c:700 > #8 0x00005555555a36cb in cmd_grep (argc=0, argv=0x7fffffffdf40, prefix=0x0) at builtin/grep.c:1257 > #9 0x000055555556603b in run_builtin (p=0x5555559b3ad8 <commands+984>, argc=4, argv=0x7fffffffdf40) at git.c:373 > #10 0x00005555555662bc in handle_builtin (argc=4, argv=0x7fffffffdf40) at git.c:572 > #11 0x000055555556641a in run_argv (argcp=0x7fffffffddfc, argv=0x7fffffffddf0) at git.c:630 > #12 0x00005555555665a8 in cmd_main (argc=4, argv=0x7fffffffdf40) at git.c:702 > #13 0x00005555555fde47 in main (argc=7, argv=0x7fffffffdf28) at common-main.c:40 > > So is_submodule_populated() needs to take a lock. But what's really > gross is that the _other_ threads need to lock just to call lstat(). > Presumably it could be done as a reader/writer type of lock where many > "reader" threads can take the "I need to lstat()" lock simultaneously, > but block when an "I'm going to chdir()" writer holds it. > > -Peff Oh interesting, I wonder if there is a way to not have to perform a chdir since taking a lock to lstat wouldn't be ideal. Thanks for helping out with this! -- Brandon Williams