* Re: Lock problems in linux/tools/perf/util/dso.c
[not found] <4C0186FE-729D-4F77-947D-11933BA38818@gmail.com>
@ 2021-12-29 19:08 ` Namhyung Kim
2021-12-30 2:42 ` Ryan Cai
0 siblings, 1 reply; 3+ messages in thread
From: Namhyung Kim @ 2021-12-29 19:08 UTC (permalink / raw)
To: Ryan Cai
Cc: Adrian Hunter, Peter Zijlstra, Arnaldo Carvalho de Melo,
Mark Rutland, Alexander Shishkin, Song Liu, Yonghong Song,
linux-kernel, netdev
Hello,
On Wed, Dec 22, 2021 at 3:33 AM Ryan Cai <ycaibb@gmail.com> wrote:
>
> Hi, I found a potential lock problem in dso_data_get_fd. Because the inconsistent branch conditions of pthread_mutex_lock(&dso__data_open_lock) and pthread_mutex_unlock(&dso__data_open_lock), it is possible that the lock dso__data_open_lock is not released in the dso_data_get_fd. Also, I have a question on why the branch condition of pthread_mutex_lock(&dso__data_open_lock) is <0. I think that the branch condition should be !=0, because pthread_mutex_lock would return 0 when succeeding. Looking forward to further discussion. One this bug is confirmed, I can send a patch.
Please fix your mail client to wrap around 80 characters.
1. dso__data_get_fd() should be paired with dso__data_put_fd()
when it returns non-negative. It'd unlock the mutex.
2. I've checked the man page and it seems you're right.
It just says that it'd return an error number or zero.
https://linux.die.net/man/3/pthread_mutex_lock
Thanks,
Namhyung
>
>
>
> https://github.com/torvalds/linux/blob/e851dfae4371d3c751f1e18e8eb5eba993de1467/tools/perf/util/dso.c#L708-L722
>
>
>
> Best,
>
> Ryan
>
>
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Lock problems in linux/tools/perf/util/dso.c
2021-12-29 19:08 ` Lock problems in linux/tools/perf/util/dso.c Namhyung Kim
@ 2021-12-30 2:42 ` Ryan Cai
2022-01-04 19:33 ` Namhyung Kim
0 siblings, 1 reply; 3+ messages in thread
From: Ryan Cai @ 2021-12-30 2:42 UTC (permalink / raw)
To: Namhyung Kim
Cc: Adrian Hunter, Peter Zijlstra, Arnaldo Carvalho de Melo,
Mark Rutland, Alexander Shishkin, Song Liu, Yonghong Song,
linux-kernel, netdev
Hi, Namhyung,
1. Indeed, I got wrong here.
2. Yes, the branch should be if (pthread_mutex_lock(&dso__data_open_lock))
instead of if (pthread_mutex_lock(&dso__data_open_lock) < 0).
Could I send a patch?
Best,
Ryan
On 30/12/2021, 3:08 AM, "Namhyung Kim" <namhyung@kernel.org> wrote:
Hello,
On Wed, Dec 22, 2021 at 3:33 AM Ryan Cai <ycaibb@gmail.com> wrote:
>
> Hi, I found a potential lock problem in dso_data_get_fd. Because the inconsistent branch conditions of pthread_mutex_lock(&dso__data_open_lock) and pthread_mutex_unlock(&dso__data_open_lock), it is possible that the lock dso__data_open_lock is not released in the dso_data_get_fd. Also, I have a question on why the branch condition of pthread_mutex_lock(&dso__data_open_lock) is <0. I think that the branch condition should be !=0, because pthread_mutex_lock would return 0 when succeeding. Looking forward to further discussion. One this bug is confirmed, I can send a patch.
Please fix your mail client to wrap around 80 characters.
1. dso__data_get_fd() should be paired with dso__data_put_fd()
when it returns non-negative. It'd unlock the mutex.
2. I've checked the man page and it seems you're right.
It just says that it'd return an error number or zero.
https://linux.die.net/man/3/pthread_mutex_lock
Thanks,
Namhyung
>
>
>
> https://github.com/torvalds/linux/blob/e851dfae4371d3c751f1e18e8eb5eba993de1467/tools/perf/util/dso.c#L708-L722
>
>
>
> Best,
>
> Ryan
>
>
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Lock problems in linux/tools/perf/util/dso.c
2021-12-30 2:42 ` Ryan Cai
@ 2022-01-04 19:33 ` Namhyung Kim
0 siblings, 0 replies; 3+ messages in thread
From: Namhyung Kim @ 2022-01-04 19:33 UTC (permalink / raw)
To: Ryan Cai
Cc: Adrian Hunter, Peter Zijlstra, Arnaldo Carvalho de Melo,
Mark Rutland, Alexander Shishkin, Song Liu, Yonghong Song,
linux-kernel, netdev
On Wed, Dec 29, 2021 at 6:42 PM Ryan Cai <ycaibb@gmail.com> wrote:
>
> Hi, Namhyung,
>
> 1. Indeed, I got wrong here.
> 2. Yes, the branch should be if (pthread_mutex_lock(&dso__data_open_lock))
> instead of if (pthread_mutex_lock(&dso__data_open_lock) < 0).
>
> Could I send a patch?
Sure!
Thanks,
Namhyung
^ permalink raw reply [flat|nested] 3+ messages in thread
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[not found] <4C0186FE-729D-4F77-947D-11933BA38818@gmail.com>
2021-12-29 19:08 ` Lock problems in linux/tools/perf/util/dso.c Namhyung Kim
2021-12-30 2:42 ` Ryan Cai
2022-01-04 19:33 ` Namhyung Kim
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