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author | Matheus Tavares <matheus.bernardino@usp.br> | 2020-01-16 05:39:49 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2020-01-18 00:52:14 +0300 |
commit | c3a5bb31c1567edd1671b54726d4acbb10563a2c (patch) | |
tree | 24732665ef6a84d45481b374c5e3f34f45ce135b /grep.c | |
parent | d0654dc308b0ba76dd8ed7bbb33c8d8f7aacd783 (diff) |
grep: fix race conditions on userdiff calls
git-grep uses an internal grep_read_mutex to protect object reading
operations. Similarly, there's a grep_attr_mutex to protect calls to the
gitattributes machinery. However, two of the three functions protected
by the last mutex may also perform object reading, as seen below:
- userdiff_get_textconv() > notes_cache_init() >
notes_cache_match_validity() > lookup_commit_reference_gently() >
parse_object() > repo_has_object_file() >
repo_has_object_file_with_flags() > oid_object_info_extended()
- userdiff_find_by_path() > git_check_attr() > collect_some_attrs() >
prepare_attr_stack() > read_attr() > read_attr_from_index() >
read_blob_data_from_index() > read_object_file()
As these calls are not protected by grep_read_mutex, there might be race
conditions with other threads performing object reading (e.g. threads
calling fill_textconv() at grep.c:fill_textconv_grep()). To prevent
that, let's make sure to acquire the lock before both of these calls.
Note: this patch might slow down the threaded grep in worktree, for the
sake of thread-safeness. However, in the following patches, we should
regain performance by replacing grep_read_mutex for an internal object
reading lock and allowing parallel inflation during object reading.
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'grep.c')
-rw-r--r-- | grep.c | 7 |
1 files changed, 6 insertions, 1 deletions
@@ -1816,7 +1816,9 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle * is not thread-safe. */ grep_attr_lock(); + grep_read_lock(); textconv = userdiff_get_textconv(opt->repo, gs->driver); + grep_read_unlock(); grep_attr_unlock(); } @@ -2184,8 +2186,11 @@ void grep_source_load_driver(struct grep_source *gs, return; grep_attr_lock(); - if (gs->path) + if (gs->path) { + grep_read_lock(); gs->driver = userdiff_find_by_path(istate, gs->path); + grep_read_unlock(); + } if (!gs->driver) gs->driver = userdiff_find_by_name("default"); grep_attr_unlock(); |