[v2,1/4] support: Add support_wait_for_thread_exit
Checks
| Context |
Check |
Description |
| dj/TryBot-apply_patch |
success
|
Patch applied to master at the time it was sent
|
Commit Message
---
v2: Makefile update, make it clearer where the wait operation with
pidfd_open would be put (it would replace the short usleep call).
support/Makefile | 3 +-
support/support.h | 4 ++
support/support_wait_for_thread_exit.c | 72 ++++++++++++++++++++++++++
3 files changed, 78 insertions(+), 1 deletion(-)
create mode 100644 support/support_wait_for_thread_exit.c
Comments
* Florian Weimer via Libc-alpha:
> + int task_tid = atoi (e->d_name);
> + if (task_tid <= 0)
> + FAIL_EXIT1 ("Invalid /proc/self/task entry: %s", e->d_name);
There's a kernel bug that causes /proc/self/task/0 to be listed
due to concurrent task exit in the kernel.
=====FAIL: nptl/tst-pthread_cancel-exited.out=====
error: support_wait_for_thread_exit.c:51: Invalid /proc/self/task entry: 0
error: 1 test failures
=====FAIL: nptl/tst-pthread_cancel-exited.test-result=====
Should work around this in our test code?
Thanks,
Florian
On 29/09/2021 17:27, Florian Weimer via Libc-alpha wrote:
> * Florian Weimer via Libc-alpha:
>
>> + int task_tid = atoi (e->d_name);
>> + if (task_tid <= 0)
>> + FAIL_EXIT1 ("Invalid /proc/self/task entry: %s", e->d_name);
>
> There's a kernel bug that causes /proc/self/task/0 to be listed
> due to concurrent task exit in the kernel.
>
> =====FAIL: nptl/tst-pthread_cancel-exited.out=====
> error: support_wait_for_thread_exit.c:51: Invalid /proc/self/task entry: 0
> error: 1 test failures
> =====FAIL: nptl/tst-pthread_cancel-exited.test-result=====
>
> Should work around this in our test code?
I have see this failures in some tests run and I was about to bring
this to you. Can we safely mitigate it by ignoring the tid '0'?
* Adhemerval Zanella:
> On 29/09/2021 17:27, Florian Weimer via Libc-alpha wrote:
>> * Florian Weimer via Libc-alpha:
>>
>>> + int task_tid = atoi (e->d_name);
>>> + if (task_tid <= 0)
>>> + FAIL_EXIT1 ("Invalid /proc/self/task entry: %s", e->d_name);
>>
>> There's a kernel bug that causes /proc/self/task/0 to be listed
>> due to concurrent task exit in the kernel.
>>
>> =====FAIL: nptl/tst-pthread_cancel-exited.out=====
>> error: support_wait_for_thread_exit.c:51: Invalid /proc/self/task entry: 0
>> error: 1 test failures
>> =====FAIL: nptl/tst-pthread_cancel-exited.test-result=====
>>
>> Should work around this in our test code?
>
> I have see this failures in some tests run and I was about to bring
> this to you. Can we safely mitigate it by ignoring the tid '0'?
Right, I have sent a patch:
[PATCH] support: Add check for TID zero in support_wait_for_thread_exit
<https://sourceware.org/pipermail/libc-alpha/2021-September/131560.html>
Thanks,
Florian
@@ -82,9 +82,10 @@ libsupport-routines = \
support_test_compare_blob \
support_test_compare_failure \
support_test_compare_string \
- support_write_file_string \
support_test_main \
support_test_verify_impl \
+ support_wait_for_thread_exit \
+ support_write_file_string \
temp_file \
timespec \
timespec-time64 \
@@ -174,6 +174,10 @@ timer_t support_create_timer (uint64_t sec, long int nsec, bool repeat,
/* Disable the timer TIMER. */
void support_delete_timer (timer_t timer);
+/* Wait until all threads except the current thread have exited (as
+ far as the kernel is concerned). */
+void support_wait_for_thread_exit (void);
+
struct support_stack
{
void *stack;
new file mode 100644
@@ -0,0 +1,72 @@
+/* Wait until all threads except the current thread has exited.
+ Copyright (C) 2021 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <dirent.h>
+#include <errno.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <unistd.h>
+
+void
+support_wait_for_thread_exit (void)
+{
+#ifdef __linux__
+ DIR *proc_self_task = opendir ("/proc/self/task");
+ TEST_VERIFY_EXIT (proc_self_task != NULL);
+
+ while (true)
+ {
+ errno = 0;
+ struct dirent *e = readdir (proc_self_task);
+ if (e == NULL && errno != 0)
+ FAIL_EXIT1 ("readdir: %m");
+ if (e == NULL)
+ {
+ /* Only the main thread remains. Testing may continue. */
+ closedir (proc_self_task);
+ return;
+ }
+
+ if (strcmp (e->d_name, ".") == 0 || strcmp (e->d_name, "..") == 0)
+ continue;
+
+ int task_tid = atoi (e->d_name);
+ if (task_tid <= 0)
+ FAIL_EXIT1 ("Invalid /proc/self/task entry: %s", e->d_name);
+
+ if (task_tid == gettid ())
+ /* The current thread. Keep scanning for other
+ threads. */
+ continue;
+
+ /* task_tid does not refer to this thread here, i.e., there is
+ another running thread. */
+
+ /* Small timeout to give the thread a chance to exit. */
+ usleep (50 * 1000);
+
+ /* Start scanning the directory from the start. */
+ rewinddir (proc_self_task);
+ }
+#else
+ /* Use a large timeout because we cannot verify that the thread has
+ exited. */
+ usleep (5 * 1000 * 1000);
+#endif
+}