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From: Tom de Vries <vries@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] [gdb] Block SIGTERM in worker threads Date: Thu, 30 Jun 2022 11:31:09 +0000 (GMT) [thread overview] Message-ID: <20220630113109.6803938485A7@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6418644b0d09af7d1334cc034a7bf8674c061d6e commit 6418644b0d09af7d1334cc034a7bf8674c061d6e Author: Tom de Vries <tdevries@suse.de> Date: Thu Jun 30 13:31:06 2022 +0200 [gdb] Block SIGTERM in worker threads With gdb build with gcc-12 and -fsanitize=thread, and test-case gdb.base/gdb-sigterm.exp, I run into: ... WARNING: ThreadSanitizer: data race (pid=9722)^M Write of size 4 at 0x00000325bc68 by thread T1:^M #0 handle_sigterm(int) src/gdb/event-top.c:1211 (gdb+0x8ec01f)^M ... Previous read of size 4 at 0x00000325bc68 by main thread:^M [failed to restore the stack]^M ^M Location is global 'sync_quit_force_run' of size 4 at \ 0x00000325bc68 (gdb+0x325bc68)^M ... SUMMARY: ThreadSanitizer: data race gdb/event-top.c:1211 in \ handle_sigterm(int)^M ... and 3 more data races involving handle_sigterm and locations: - active_ext_lang - quit_flag - heap block of size 40 (XNEW (async_signal_handler) in create_async_signal_handler) This was reported in PR29297. The testcase executes a "kill -TERM $gdb_pid", which generates a process-directed signal. A process-directed signal can be delivered to any thread, and what we see here is the fallout of the signal being delivered to a worker thread rather than the main thread. Fix this by blocking SIGTERM in the worker threads. [ I have not been able to reproduce this after it occurred for the first time, so unfortunately I cannot confirm that the patch fixes the problem. ] Tested on x86_64-linux, with and without -fsanitize=thread. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29297 Diff: --- gdbsupport/block-signals.h | 1 + 1 file changed, 1 insertion(+) diff --git a/gdbsupport/block-signals.h b/gdbsupport/block-signals.h index cf97208c750..4703690a4ec 100644 --- a/gdbsupport/block-signals.h +++ b/gdbsupport/block-signals.h @@ -42,6 +42,7 @@ public: sigaddset (&mask, SIGCHLD); sigaddset (&mask, SIGALRM); sigaddset (&mask, SIGWINCH); + sigaddset (&mask, SIGTERM); gdb_sigmask (SIG_BLOCK, &mask, &m_old_mask); #endif }
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