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| author |  Jeff Hostetler <jeffhost@microsoft.com> | 2017-09-06 15:43:48 +0000 |
|---|---|---|
| committer |  Junio C Hamano <gitster@pobox.com> | 2017-09-07 09:42:02 +0900 |
| commit | 8b604d19515c4be18403047045faa363d4de217b (patch) | |
| tree | 5bb6fb5e265c3f46c0a08b498c6ee2159dc326cc /t/helper | |
| parent | The fifth batch post 2.14 (diff) | |
| download | tgif-8b604d19515c4be18403047045faa363d4de217b.tar.xz | |
hashmap: add API to disable item counting when threaded
This is to address concerns raised by ThreadSanitizer on the mailing list
about threaded unprotected R/W access to map.size with my previous "disallow
rehash" change (0607e10009ee4e37cb49b4cec8d28a9dda1656a4).
See:
https://public-inbox.org/git/adb37b70139fd1e2bac18bfd22c8b96683ae18eb.1502780344.git.martin.agren@gmail.com/
Add API to hashmap to disable item counting and thus automatic rehashing.
Also include API to later re-enable them.
When item counting is disabled, the map.size field is invalid. So to
prevent accidents, the field has been renamed and an accessor function
hashmap_get_size() has been added. All direct references to this
field have been been updated. And the name of the field changed
to map.private_size to communicate this.
Here is the relevant output from ThreadSanitizer showing the problem:
WARNING: ThreadSanitizer: data race (pid=10554)
Read of size 4 at 0x00000082d488 by thread T2 (mutexes: write M16):
#0 hashmap_add hashmap.c:209
#1 hash_dir_entry_with_parent_and_prefix name-hash.c:302
#2 handle_range_dir name-hash.c:347
#3 handle_range_1 name-hash.c:415
#4 lazy_dir_thread_proc name-hash.c:471
#5 <null> <null>
Previous write of size 4 at 0x00000082d488 by thread T1 (mutexes: write M31):
#0 hashmap_add hashmap.c:209
#1 hash_dir_entry_with_parent_and_prefix name-hash.c:302
#2 handle_range_dir name-hash.c:347
#3 handle_range_1 name-hash.c:415
#4 handle_range_dir name-hash.c:380
#5 handle_range_1 name-hash.c:415
#6 lazy_dir_thread_proc name-hash.c:471
#7 <null> <null>
Martin gives instructions for running TSan on test t3008 in this post:
https://public-inbox.org/git/CAN0heSoJDL9pWELD6ciLTmWf-a=oyxe4EXXOmCKvsG5MSuzxsA@mail.gmail.com/
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 't/helper')
| -rw-r--r-- | t/helper/test-hashmap.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/t/helper/test-hashmap.c b/t/helper/test-hashmap.c index 6004c81f0b..1145d51671 100644 --- a/t/helper/test-hashmap.c +++ b/t/helper/test-hashmap.c @@ -235,7 +235,8 @@ int cmd_main(int argc, const char **argv) } else if (!strcmp("size", cmd)) { /* print table sizes */ - printf("%u %u\n", map.tablesize, map.size); + printf("%u %u\n", map.tablesize, + hashmap_get_size(&map)); } else if (!strcmp("intern", cmd) && l1) { |