From: Simon Marchi <simon.marchi@polymtl.ca>
To: John Baldwin <jhb@FreeBSD.org>, gdb-patches@sourceware.org
Subject: Re: [PATCH v5 06/15] do_target_wait_1: Clear TARGET_WNOHANG if the target isn't async.
Date: Wed, 23 Feb 2022 10:51:02 -0500 [thread overview]
Message-ID: <1c29b477-e34b-bab0-7430-b506a8de18c2@polymtl.ca> (raw)
In-Reply-To: <8300cb6a-c0d7-a2b7-ee20-f6eabb1c7d82@polymtl.ca>
On 2022-02-22 20:40, Simon Marchi via Gdb-patches wrote:
>
>
> On 2022-02-22 19:07, John Baldwin wrote:
>> I have no idea why these tests didn't run in my VM. If you revert just this
>> commit and keep the rest of the series do you see any other regressions?
>
> If I revert this commit, the testsuite goes back to "no regressions" for me.
Here's what happens:
1. On remote inferior was started, is now stopped. It is not "async",
because when everything is stopped, the async fd is removed from the
event loop, but it "can async".
2. We run a native inferior, the event loop gets woken up by the native
target's fd.
3. In do_target_wait, we randomly choose an inferior to call target_wait
on first, it happens to be the remote inferior.
4. Because the target is currently not "async", we clear
TARGET_WNOHANG, resulting in synchronous wait. We therefore block
here:
#0 0x00007fe9540dbb4d in select () from /usr/lib/libc.so.6
#1 0x000055fc7e821da7 in gdb_select (n=15, readfds=0x7ffdb77c1fb0, writefds=0x0, exceptfds=0x7ffdb77c2050, timeout=0x7ffdb77c1f90) at /home/simark/src/binutils-gdb/gdb/posix-hdep.c:31
#2 0x000055fc7ddef905 in interruptible_select (n=15, readfds=0x7ffdb77c1fb0, writefds=0x0, exceptfds=0x7ffdb77c2050, timeout=0x7ffdb77c1f90) at /home/simark/src/binutils-gdb/gdb/event-top.c:1134
#3 0x000055fc7eda58e4 in ser_base_wait_for (scb=0x6250002e4100, timeout=1) at /home/simark/src/binutils-gdb/gdb/ser-base.c:240
#4 0x000055fc7eda66ba in do_ser_base_readchar (scb=0x6250002e4100, timeout=-1) at /home/simark/src/binutils-gdb/gdb/ser-base.c:365
#5 0x000055fc7eda6ff6 in generic_readchar (scb=0x6250002e4100, timeout=-1, do_readchar=0x55fc7eda663c <do_ser_base_readchar(serial*, int)>) at /home/simark/src/binutils-gdb/gdb/ser-base.c:444
#6 0x000055fc7eda718a in ser_base_readchar (scb=0x6250002e4100, timeout=-1) at /home/simark/src/binutils-gdb/gdb/ser-base.c:471
#7 0x000055fc7edb1ecd in serial_readchar (scb=0x6250002e4100, timeout=-1) at /home/simark/src/binutils-gdb/gdb/serial.c:393
#8 0x000055fc7ec48b8f in remote_target::readchar (this=0x617000038780, timeout=-1) at /home/simark/src/binutils-gdb/gdb/remote.c:9446
#9 0x000055fc7ec4da82 in remote_target::getpkt_or_notif_sane_1 (this=0x617000038780, buf=0x6170000387a8, forever=1, expecting_notif=1, is_notif=0x7ffdb77c24f0) at /home/simark/src/binutils-gdb/gdb/remote.c:9928
#10 0x000055fc7ec4f045 in remote_target::getpkt_or_notif_sane (this=0x617000038780, buf=0x6170000387a8, forever=1, is_notif=0x7ffdb77c24f0) at /home/simark/src/binutils-gdb/gdb/remote.c:10037
#11 0x000055fc7ec354d4 in remote_target::wait_ns (this=0x617000038780, ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/remote.c:8147
#12 0x000055fc7ec38aa1 in remote_target::wait (this=0x617000038780, ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/remote.c:8337
#13 0x000055fc7f1409ce in target_wait (ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/target.c:2612
#14 0x000055fc7e19da98 in do_target_wait_1 (inf=0x617000038080, ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:3636
#15 0x000055fc7e19e26b in operator() (__closure=0x7ffdb77c2f90, inf=0x617000038080) at /home/simark/src/binutils-gdb/gdb/infrun.c:3697
#16 0x000055fc7e19f0c4 in do_target_wait (ecs=0x7ffdb77c33a0, options=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:3716
#17 0x000055fc7e1a31f7 in fetch_inferior_event () at /home/simark/src/binutils-gdb/gdb/infrun.c:4061
Normally, the wait on the remote target would return nothing, so we
would then wait on the native target and fetch its event.
Simon
next prev parent reply other threads:[~2022-02-23 15:51 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-21 20:16 [PATCH v5 00/15] FreeBSD target async mode and related refactoring John Baldwin
2022-01-21 20:16 ` [PATCH v5 01/15] gdbsupport: Add an event-pipe class John Baldwin
2022-01-21 20:16 ` [PATCH v5 02/15] gdb linux-nat: Convert linux_nat_event_pipe to the event_pipe class John Baldwin
2022-01-21 20:16 ` [PATCH v5 03/15] gdbserver linux-low: Convert linux_event_pipe " John Baldwin
2022-01-21 20:16 ` [PATCH v5 04/15] Enable async mode on supported targets in target_resume John Baldwin
2022-02-20 10:47 ` Joel Brobecker
2022-01-21 20:16 ` [PATCH v5 05/15] Don't enable async mode at the end of target ::resume methods John Baldwin
2022-02-20 10:49 ` Joel Brobecker
2022-01-21 20:16 ` [PATCH v5 06/15] do_target_wait_1: Clear TARGET_WNOHANG if the target isn't async John Baldwin
2022-02-22 22:38 ` Simon Marchi
2022-02-23 0:07 ` John Baldwin
2022-02-23 1:40 ` Simon Marchi
2022-02-23 15:51 ` Simon Marchi [this message]
2022-02-23 16:12 ` John Baldwin
2022-02-24 2:46 ` Simon Marchi
2022-02-24 19:02 ` John Baldwin
2022-02-24 19:16 ` Simon Marchi
2022-01-21 20:16 ` [PATCH v5 07/15] inf-ptrace: Return an IGNORE event if waitpid() fails John Baldwin
2022-02-20 11:38 ` Joel Brobecker
2022-01-21 20:16 ` [PATCH v5 08/15] inf-ptrace: Support async targets in inf_ptrace_target::wait John Baldwin
2022-01-21 20:16 ` [PATCH v5 09/15] fbsd-nat: Implement async target support John Baldwin
2022-01-21 20:16 ` [PATCH v5 10/15] fbsd-nat: Include ptrace operation in error messages John Baldwin
2022-01-21 20:16 ` [PATCH v5 11/15] fbsd-nat: Various cleanups to the ::resume entry debug message John Baldwin
2022-01-21 20:16 ` [PATCH v5 12/15] fbsd-nat: Return nullptr rather than failing ::thread_name John Baldwin
2022-01-21 20:16 ` [PATCH v5 13/15] Enable async mode in the target in attach_cmd John Baldwin
2022-01-21 20:16 ` [PATCH v5 14/15] inf-ptrace: Add an event_pipe to be used for async mode in subclasses John Baldwin
2022-01-21 20:16 ` [PATCH v5 15/15] NEWS: Note that the FreeBSD async target supports async mode John Baldwin
2022-01-22 6:28 ` Eli Zaretskii
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