Re: [PATCH][gdb] Block SIGTERM in worker threads

[Pedro Alves <pedro@palves.net>]

On 2022-06-30 10:58, Tom de Vries wrote:
> Hi,
> 
> 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.
> 
> Any comments?

OK.