From: Stefan Beller <sbeller@google.com>
To: "Martin Ågren" <martin.agren@gmail.com>
Cc: "git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: tsan: t5400: set_try_to_free_routine
Date: Tue, 15 Aug 2017 10:35:00 -0700 [thread overview]
Message-ID: <CAGZ79kYbPvmqV1PR_NjxLbp2vqC6=JdP+-hzdwQvUmVLZU_Wtg@mail.gmail.com> (raw)
In-Reply-To: <939b37f809dd9e1526593c02154fae14b369c73a.1502780344.git.martin.agren@gmail.com>
On Tue, Aug 15, 2017 at 5:53 AM, Martin Ågren <martin.agren@gmail.com> wrote:
> Using SANITIZE=thread made t5400-send-pack.sh hit the potential race
> below.
>
> This is set_try_to_free_routine in wrapper.c. The race relates to the
> reading of the "old" value. The caller doesn't care about the "old"
> value, so this should be harmless right now. But it seems that using
> this mechanism from multiple threads and restoring the earlier value
> will probably not work out every time. (Not necessarily because of the
> race in set_try_to_free_routine, but, e.g., because callers might not
> restore the function pointer in the reverse order of how they
> originally set it.)
>
> Properly "fixing" this for thread-safety would probably require some
> redesigning, which at the time might not be warranted. I'm just posting
> this for completeness.
Maybe related read (also error handling in threads):
https://public-inbox.org/git/20170619220036.22656-1-avarab@gmail.com/
>
> Martin
>
> WARNING: ThreadSanitizer: data race (pid=21382)
> Read of size 8 at 0x000000979970 by thread T1:
> #0 set_try_to_free_routine wrapper.c:35 (git+0x0000006cde1c)
> #1 prepare_trace_line trace.c:105 (git+0x0000006a3bf0)
> #2 trace_strbuf_fl trace.c:185 (git+0x0000006a3bf0)
> #3 packet_trace pkt-line.c:80 (git+0x0000005f9f43)
> #4 packet_read pkt-line.c:309 (git+0x0000005fbe10)
> #5 recv_sideband sideband.c:37 (git+0x000000684c5e)
> #6 sideband_demux send-pack.c:216 (git+0x00000065a38c)
> #7 run_thread run-command.c:933 (git+0x000000655a93)
> #8 <null> <null> (libtsan.so.0+0x0000000230d9)
>
> Previous write of size 8 at 0x000000979970 by main thread:
> #0 set_try_to_free_routine wrapper.c:38 (git+0x0000006cde39)
> #1 prepare_trace_line trace.c:105 (git+0x0000006a3bf0)
> #2 trace_strbuf_fl trace.c:185 (git+0x0000006a3bf0)
> #3 packet_trace pkt-line.c:80 (git+0x0000005f9f43)
> #4 packet_read pkt-line.c:324 (git+0x0000005fc0bb)
> #5 packet_read_line_generic pkt-line.c:332 (git+0x0000005fc0bb)
> #6 packet_read_line pkt-line.c:342 (git+0x0000005fc0bb)
> #7 receive_unpack_status send-pack.c:149 (git+0x00000065c1e4)
> #8 send_pack send-pack.c:581 (git+0x00000065c1e4)
> #9 git_transport_push transport.c:574 (git+0x0000006ab2c1)
> #10 transport_push transport.c:1068 (git+0x0000006ae5d5)
> #11 push_with_options builtin/push.c:336 (git+0x00000049d580)
> #12 do_push builtin/push.c:419 (git+0x00000049f57d)
> #13 cmd_push builtin/push.c:591 (git+0x00000049f57d)
> #14 run_builtin git.c:330 (git+0x00000040949e)
> #15 handle_builtin git.c:538 (git+0x00000040949e)
> #16 run_argv git.c:590 (git+0x000000409a0e)
> #17 cmd_main git.c:667 (git+0x000000409a0e)
> #18 main common-main.c:43 (git+0x0000004079d1)
>
> Location is global 'try_to_free_routine' of size 8 at 0x000000979970 (git+0x000000979970)
>
> Thread T1 (tid=21405, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 start_async run-command.c:1130 (git+0x0000006582e7)
> #2 send_pack send-pack.c:562 (git+0x00000065b7c8)
> #3 git_transport_push transport.c:574 (git+0x0000006ab2c1)
> #4 transport_push transport.c:1068 (git+0x0000006ae5d5)
> #5 push_with_options builtin/push.c:336 (git+0x00000049d580)
> #6 do_push builtin/push.c:419 (git+0x00000049f57d)
> #7 cmd_push builtin/push.c:591 (git+0x00000049f57d)
> #8 run_builtin git.c:330 (git+0x00000040949e)
> #9 handle_builtin git.c:538 (git+0x00000040949e)
> #10 run_argv git.c:590 (git+0x000000409a0e)
> #11 cmd_main git.c:667 (git+0x000000409a0e)
> #12 main common-main.c:43 (git+0x0000004079d1)
>
> SUMMARY: ThreadSanitizer: data race wrapper.c:35 set_try_to_free_routine
>
next prev parent reply other threads:[~2017-08-15 17:35 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-15 12:53 [PATCH/RFC 0/5] Some ThreadSanitizer-results Martin Ågren
2017-08-15 12:53 ` [PATCH 1/5] convert: initialize attr_action in convert_attrs Martin Ågren
2017-08-15 14:17 ` Torsten Bögershausen
2017-08-15 14:29 ` Torsten Bögershausen
2017-08-15 14:40 ` Martin Ågren
2017-08-15 12:53 ` [PATCH 2/5] pack-objects: take lock before accessing `remaining` Martin Ågren
2017-08-15 19:50 ` Johannes Sixt
2017-08-15 12:53 ` [PATCH 3/5] Makefile: define GIT_THREAD_SANITIZER Martin Ågren
2017-08-15 12:53 ` [PATCH 4/5] strbuf_reset: don't write to slopbuf with ThreadSanitizer Martin Ågren
2017-08-15 18:43 ` Junio C Hamano
2017-08-15 19:06 ` Martin Ågren
2017-08-15 19:19 ` Junio C Hamano
2017-08-15 12:53 ` [PATCH 5/5] ThreadSanitizer: add suppressions Martin Ågren
2017-08-15 12:53 ` tsan: t3008: hashmap_add touches size from multiple threads Martin Ågren
2017-08-15 17:59 ` Jeff Hostetler
2017-08-15 18:17 ` Stefan Beller
2017-08-15 18:40 ` Martin Ågren
2017-08-15 18:48 ` Stefan Beller
2017-08-15 19:21 ` Martin Ågren
2017-08-15 20:46 ` Jeff Hostetler
2017-08-30 18:59 ` [PATCH] hashmap: address ThreadSanitizer concerns Jeff Hostetler
2017-08-30 18:59 ` [PATCH] hashmap: add API to disable item counting when threaded Jeff Hostetler
2017-09-01 23:31 ` Johannes Schindelin
2017-09-01 23:50 ` Jonathan Nieder
2017-09-05 16:39 ` Jeff Hostetler
2017-09-05 17:13 ` Martin Ågren
2017-09-02 8:17 ` Jeff King
2017-09-04 15:59 ` Johannes Schindelin
2017-09-05 16:54 ` Jeff Hostetler
2017-09-06 3:43 ` Junio C Hamano
2017-09-05 16:33 ` Jeff Hostetler
2017-09-02 8:05 ` Jeff King
2017-09-05 17:07 ` Jeff Hostetler
2017-09-02 8:39 ` Simon Ruderich
2017-09-06 1:24 ` Junio C Hamano
2017-09-06 15:33 ` Jeff Hostetler
2017-09-06 15:43 ` [PATCH v2] hashmap: address ThreadSanitizer concerns Jeff Hostetler
2017-09-06 15:43 ` [PATCH v2] hashmap: add API to disable item counting when threaded Jeff Hostetler
2017-08-15 12:53 ` tsan: t5400: set_try_to_free_routine Martin Ågren
2017-08-15 17:35 ` Stefan Beller [this message]
2017-08-15 18:44 ` Martin Ågren
2017-08-17 10:57 ` Jeff King
2017-08-20 10:06 ` [PATCH/RFC 0/5] Some ThreadSanitizer-results Jeff King
2017-08-20 10:45 ` Martin Ågren
2017-08-21 17:43 ` [PATCH v2 0/4] " Martin Ågren
2017-08-21 17:43 ` [PATCH v2 1/4] convert: always initialize attr_action in convert_attrs Martin Ågren
2017-08-21 17:43 ` [PATCH v2 2/4] pack-objects: take lock before accessing `remaining` Martin Ågren
2017-08-21 17:43 ` [PATCH v2 3/4] strbuf_setlen: don't write to strbuf_slopbuf Martin Ågren
2017-08-23 17:24 ` Junio C Hamano
2017-08-23 17:43 ` Martin Ågren
2017-08-23 18:30 ` Junio C Hamano
2017-08-23 20:37 ` Brandon Casey
2017-08-23 21:04 ` Junio C Hamano
2017-08-23 21:20 ` Brandon Casey
2017-08-23 21:54 ` Brandon Casey
2017-08-23 22:11 ` Brandon Casey
2017-08-24 16:52 ` Junio C Hamano
2017-08-24 18:29 ` Brandon Casey
2017-08-24 19:16 ` Martin Ågren
2017-08-23 22:24 ` Junio C Hamano
2017-08-23 22:39 ` Brandon Casey
2017-08-21 17:43 ` [PATCH v2 4/4] ThreadSanitizer: add suppressions Martin Ågren
2017-08-25 17:04 ` Jeff King
2017-08-28 20:56 ` [PATCH v2 0/4] Some ThreadSanitizer-results Jeff Hostetler
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