* [PATCH] [gdb/server] Emit warning for SIGINT failure
@ 2022-11-09 20:32 Tom de Vries
2022-11-26 13:34 ` [PING] " Tom de Vries
2022-11-26 20:29 ` Simon Marchi
0 siblings, 2 replies; 4+ messages in thread
From: Tom de Vries @ 2022-11-09 20:32 UTC (permalink / raw)
To: gdb-patches
Consider the executable from test-case gdb.base/interrupt-daemon.exp.
When starting it using gdbserver:
...
$ ./build/gdbserver/gdbserver localhost:2345 \
./outputs/gdb.base/interrupt-daemon/interrupt-daemon
...
and connecting to it using gdb:
...
$ gdb -q -ex "target remote localhost:2345" \
-ex "set follow-fork-mode child" \
-ex "break daemon_main" -ex cont
...
we are setup to do the same as in the test-case: interrupt a running inferior
using ^C.
So let's try:
...
(gdb) continue
Continuing.
^C
...
After pressing ^C, nothing happens. This a known problem, filed as
PR remote/18772.
The problem is that in linux_process_target::request_interrupt, a kill is used
to send a SIGINT, but it fails. And it fails silently.
Make the failure verbose by adding a warning, such that the gdbserver output
becomes more helpful:
...
Process interrupt-daemon created; pid = 15068
Listening on port 2345
Remote debugging from host ::1, port 35148
Detaching from process 15068
Detaching from process 15085
gdbserver: Sending SIGINT to process group of pid 15068 failed: \
No such process
...
Note that the failure can easily be reproduced using the test-case and target
board native-gdbserver:
...
(gdb) continue^M
Continuing.^M
PASS: gdb.base/interrupt-daemon.exp: fg: continue
^CFAIL: gdb.base/interrupt-daemon.exp: fg: ctrl-c stops process (timeout)
...
as reported in PR server/23382.
Tested on x86_64-linux.
---
gdbserver/linux-low.cc | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index 0cbfeb99086..f4df02d3ac9 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -5467,7 +5467,10 @@ linux_process_target::request_interrupt ()
{
/* Send a SIGINT to the process group. This acts just like the user
typed a ^C on the controlling terminal. */
- ::kill (-signal_pid, SIGINT);
+ int res = ::kill (-signal_pid, SIGINT);
+ if (res == -1)
+ warning (_("Sending SIGINT to process group of pid %ld failed: %s"),
+ signal_pid, safe_strerror (errno));
}
bool
base-commit: 3abad2f6a637a0c56af70311d94ec66eea1b4852
--
2.35.3
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PING] [PATCH] [gdb/server] Emit warning for SIGINT failure
2022-11-09 20:32 [PATCH] [gdb/server] Emit warning for SIGINT failure Tom de Vries
@ 2022-11-26 13:34 ` Tom de Vries
2022-11-26 20:29 ` Simon Marchi
1 sibling, 0 replies; 4+ messages in thread
From: Tom de Vries @ 2022-11-26 13:34 UTC (permalink / raw)
To: gdb-patches
On 11/9/22 21:32, Tom de Vries via Gdb-patches wrote:
> Consider the executable from test-case gdb.base/interrupt-daemon.exp.
>
> When starting it using gdbserver:
> ...
> $ ./build/gdbserver/gdbserver localhost:2345 \
> ./outputs/gdb.base/interrupt-daemon/interrupt-daemon
> ...
> and connecting to it using gdb:
> ...
> $ gdb -q -ex "target remote localhost:2345" \
> -ex "set follow-fork-mode child" \
> -ex "break daemon_main" -ex cont
> ...
> we are setup to do the same as in the test-case: interrupt a running inferior
> using ^C.
>
> So let's try:
> ...
> (gdb) continue
> Continuing.
> ^C
> ...
> After pressing ^C, nothing happens. This a known problem, filed as
> PR remote/18772.
>
> The problem is that in linux_process_target::request_interrupt, a kill is used
> to send a SIGINT, but it fails. And it fails silently.
>
> Make the failure verbose by adding a warning, such that the gdbserver output
> becomes more helpful:
> ...
> Process interrupt-daemon created; pid = 15068
> Listening on port 2345
> Remote debugging from host ::1, port 35148
> Detaching from process 15068
> Detaching from process 15085
> gdbserver: Sending SIGINT to process group of pid 15068 failed: \
> No such process
> ...
>
> Note that the failure can easily be reproduced using the test-case and target
> board native-gdbserver:
> ...
> (gdb) continue^M
> Continuing.^M
> PASS: gdb.base/interrupt-daemon.exp: fg: continue
> ^CFAIL: gdb.base/interrupt-daemon.exp: fg: ctrl-c stops process (timeout)
> ...
> as reported in PR server/23382.
>
> Tested on x86_64-linux.
Ping.
Thanks,
- Tom
> ---
> gdbserver/linux-low.cc | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
> index 0cbfeb99086..f4df02d3ac9 100644
> --- a/gdbserver/linux-low.cc
> +++ b/gdbserver/linux-low.cc
> @@ -5467,7 +5467,10 @@ linux_process_target::request_interrupt ()
> {
> /* Send a SIGINT to the process group. This acts just like the user
> typed a ^C on the controlling terminal. */
> - ::kill (-signal_pid, SIGINT);
> + int res = ::kill (-signal_pid, SIGINT);
> + if (res == -1)
> + warning (_("Sending SIGINT to process group of pid %ld failed: %s"),
> + signal_pid, safe_strerror (errno));
> }
>
> bool
>
> base-commit: 3abad2f6a637a0c56af70311d94ec66eea1b4852
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] [gdb/server] Emit warning for SIGINT failure
2022-11-09 20:32 [PATCH] [gdb/server] Emit warning for SIGINT failure Tom de Vries
2022-11-26 13:34 ` [PING] " Tom de Vries
@ 2022-11-26 20:29 ` Simon Marchi
2022-11-27 9:27 ` Tom de Vries
1 sibling, 1 reply; 4+ messages in thread
From: Simon Marchi @ 2022-11-26 20:29 UTC (permalink / raw)
To: Tom de Vries, gdb-patches
On 11/9/22 15:32, Tom de Vries via Gdb-patches wrote:
> Consider the executable from test-case gdb.base/interrupt-daemon.exp.
>
> When starting it using gdbserver:
> ...
> $ ./build/gdbserver/gdbserver localhost:2345 \
> ./outputs/gdb.base/interrupt-daemon/interrupt-daemon
> ...
> and connecting to it using gdb:
> ...
> $ gdb -q -ex "target remote localhost:2345" \
> -ex "set follow-fork-mode child" \
> -ex "break daemon_main" -ex cont
> ...
> we are setup to do the same as in the test-case: interrupt a running inferior
> using ^C.
>
> So let's try:
> ...
> (gdb) continue
> Continuing.
> ^C
> ...
> After pressing ^C, nothing happens. This a known problem, filed as
> PR remote/18772.
>
> The problem is that in linux_process_target::request_interrupt, a kill is used
> to send a SIGINT, but it fails. And it fails silently.
>
> Make the failure verbose by adding a warning, such that the gdbserver output
> becomes more helpful:
> ...
> Process interrupt-daemon created; pid = 15068
> Listening on port 2345
> Remote debugging from host ::1, port 35148
> Detaching from process 15068
> Detaching from process 15085
> gdbserver: Sending SIGINT to process group of pid 15068 failed: \
> No such process
> ...
>
> Note that the failure can easily be reproduced using the test-case and target
> board native-gdbserver:
> ...
> (gdb) continue^M
> Continuing.^M
> PASS: gdb.base/interrupt-daemon.exp: fg: continue
> ^CFAIL: gdb.base/interrupt-daemon.exp: fg: ctrl-c stops process (timeout)
> ...
> as reported in PR server/23382.
>
> Tested on x86_64-linux.
> ---
> gdbserver/linux-low.cc | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
> index 0cbfeb99086..f4df02d3ac9 100644
> --- a/gdbserver/linux-low.cc
> +++ b/gdbserver/linux-low.cc
> @@ -5467,7 +5467,10 @@ linux_process_target::request_interrupt ()
> {
> /* Send a SIGINT to the process group. This acts just like the user
> typed a ^C on the controlling terminal. */
> - ::kill (-signal_pid, SIGINT);
> + int res = ::kill (-signal_pid, SIGINT);
> + if (res == -1)
> + warning (_("Sending SIGINT to process group of pid %ld failed: %s"),
> + signal_pid, safe_strerror (errno));
I don't fully understand the issue about the separate process group and
all that (and I just have a few minutes so I won't dig into that right
now), but I don't see any downside to your patch. Therefore:
Approved-By: Simon Marchi <simon.marchi@efficios.com>
On a tangential note, at first glance, this use of the signal_pid global
seems bogus. If you run two inferiors, signal_pid will have the pid of
the second one. Then, if you only resume the first one and press
ctrl-c, I guess we'll send a SIGINT to the second one, that is not
resumed, and then wait for it to report a stop, which won't happen?
Simon
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] [gdb/server] Emit warning for SIGINT failure
2022-11-26 20:29 ` Simon Marchi
@ 2022-11-27 9:27 ` Tom de Vries
0 siblings, 0 replies; 4+ messages in thread
From: Tom de Vries @ 2022-11-27 9:27 UTC (permalink / raw)
To: Simon Marchi, gdb-patches
On 11/26/22 21:29, Simon Marchi wrote:
>
>
> On 11/9/22 15:32, Tom de Vries via Gdb-patches wrote:
>> Consider the executable from test-case gdb.base/interrupt-daemon.exp.
>>
>> When starting it using gdbserver:
>> ...
>> $ ./build/gdbserver/gdbserver localhost:2345 \
>> ./outputs/gdb.base/interrupt-daemon/interrupt-daemon
>> ...
>> and connecting to it using gdb:
>> ...
>> $ gdb -q -ex "target remote localhost:2345" \
>> -ex "set follow-fork-mode child" \
>> -ex "break daemon_main" -ex cont
>> ...
>> we are setup to do the same as in the test-case: interrupt a running inferior
>> using ^C.
>>
>> So let's try:
>> ...
>> (gdb) continue
>> Continuing.
>> ^C
>> ...
>> After pressing ^C, nothing happens. This a known problem, filed as
>> PR remote/18772.
>>
>> The problem is that in linux_process_target::request_interrupt, a kill is used
>> to send a SIGINT, but it fails. And it fails silently.
>>
>> Make the failure verbose by adding a warning, such that the gdbserver output
>> becomes more helpful:
>> ...
>> Process interrupt-daemon created; pid = 15068
>> Listening on port 2345
>> Remote debugging from host ::1, port 35148
>> Detaching from process 15068
>> Detaching from process 15085
>> gdbserver: Sending SIGINT to process group of pid 15068 failed: \
>> No such process
>> ...
>>
>> Note that the failure can easily be reproduced using the test-case and target
>> board native-gdbserver:
>> ...
>> (gdb) continue^M
>> Continuing.^M
>> PASS: gdb.base/interrupt-daemon.exp: fg: continue
>> ^CFAIL: gdb.base/interrupt-daemon.exp: fg: ctrl-c stops process (timeout)
>> ...
>> as reported in PR server/23382.
>>
>> Tested on x86_64-linux.
>> ---
>> gdbserver/linux-low.cc | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
>> index 0cbfeb99086..f4df02d3ac9 100644
>> --- a/gdbserver/linux-low.cc
>> +++ b/gdbserver/linux-low.cc
>> @@ -5467,7 +5467,10 @@ linux_process_target::request_interrupt ()
>> {
>> /* Send a SIGINT to the process group. This acts just like the user
>> typed a ^C on the controlling terminal. */
>> - ::kill (-signal_pid, SIGINT);
>> + int res = ::kill (-signal_pid, SIGINT);
>> + if (res == -1)
>> + warning (_("Sending SIGINT to process group of pid %ld failed: %s"),
>> + signal_pid, safe_strerror (errno));
>
> I don't fully understand the issue about the separate process group and
> all that (and I just have a few minutes so I won't dig into that right
> now), but I don't see any downside to your patch. Therefore:
>
> Approved-By: Simon Marchi <simon.marchi@efficios.com>
>
Thanks for the review, much appreciated.
> On a tangential note, at first glance, this use of the signal_pid global
> seems bogus. If you run two inferiors, signal_pid will have the pid of
> the second one. Then, if you only resume the first one and press
> ctrl-c, I guess we'll send a SIGINT to the second one, that is not
> resumed, and then wait for it to report a stop, which won't happen?
Agreed, and this warning won't trigger for that scenario, since the
signal_pid will be valid.
I don't understand at this point whether the correct pid is somewhere
available in gdbserver or needs to be passed by gdb, but unfortunately I
don't see an opportunity to look into this further before the upcoming
gdb 13 release (and the fact that this has remained unfixed for 7 years
suggests to me that it's not a trivial fix).
Thanks,
- Tom
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-11-27 9:27 ` Tom de Vries
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