Commit Message
PR build/25268 points out that the build fails on macOS, because on
macOS the "pthread_setname_np" function takes a single argument.
This patch fixes the problem, by introducing a new template adapter
function that handles both styles of pthread_setname_np. This is a
technique I learned from Alexandre Oliva, and avoids the need for a
complicated autoconf check.
This change also meant moving the pthread_setname_np call to the
thread function, because macOS only permits setting the name of the
current thread. This means that there can be a brief window when gdb
will see the wrong name; but I think this is a minor concern.
Tested by rebuilding on x86-64 Fedora 30, and on macOS High Sierra.
On Linux I also debugged gdb to ensure that the thread names are still
set correctly.
gdb/ChangeLog
2019-12-10 Tom Tromey <tromey@adacore.com>
PR build/25268:
* gdbsupport/thread-pool.c (set_thread_name): New template
function.
(thread_pool::set_thread_count): Don't call pthread_setname_np.
(thread_pool::thread_function): Call set_thread_name.
Change-Id: Id7bf28d99ca27a893a9fc87ebb90b15a9c2a9cb4
---
gdb/ChangeLog | 8 ++++++++
gdb/gdbsupport/thread-pool.c | 31 +++++++++++++++++++++++++++----
2 files changed, 35 insertions(+), 4 deletions(-)
Comments
On 2019-12-10 4:47 p.m., Tom Tromey wrote:
> PR build/25268 points out that the build fails on macOS, because on
> macOS the "pthread_setname_np" function takes a single argument.
>
> This patch fixes the problem, by introducing a new template adapter
> function that handles both styles of pthread_setname_np. This is a
> technique I learned from Alexandre Oliva, and avoids the need for a
> complicated autoconf check.
>
> This change also meant moving the pthread_setname_np call to the
> thread function, because macOS only permits setting the name of the
> current thread. This means that there can be a brief window when gdb
> will see the wrong name; but I think this is a minor concern.
>
> Tested by rebuilding on x86-64 Fedora 30, and on macOS High Sierra.
> On Linux I also debugged gdb to ensure that the thread names are still
> set correctly.
I think a version without templates would make it a bit simpler to understand:
void
set_thread_name (int (*set_name) (pthread_t, const char *), const char *name)
{
set_name (pthread_self (), name);
}
void
set_thread_name (int (*set_name) (const char *), const char *name)
{
set_name (name);
}
Also, they should probably be static, disabling -Wunused-functions, if necessary,
like in:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blobdiff;f=gdb/gdbsupport/safe-strerror.c;h=9973fa678577c3ff1d9188a6679a0c8cecfd5d26;hp=7425af590f789c1625013c9dc51b505a324ad7fd;hb=cb51113052d534b628c635ac7b86b95fe436d60d;hpb=ab7d13f07027e6232a21448ef51f0a52a96738a9
Simon
On Tue, 10 Dec 2019 14:47:17 -0700
Tom Tromey <tromey@adacore.com> wrote:
> PR build/25268 points out that the build fails on macOS, because on
> macOS the "pthread_setname_np" function takes a single argument.
>
> This patch fixes the problem, by introducing a new template adapter
> function that handles both styles of pthread_setname_np. This is a
> technique I learned from Alexandre Oliva, and avoids the need for a
> complicated autoconf check.
>
> This change also meant moving the pthread_setname_np call to the
> thread function, because macOS only permits setting the name of the
> current thread. This means that there can be a brief window when gdb
> will see the wrong name; but I think this is a minor concern.
>
> Tested by rebuilding on x86-64 Fedora 30, and on macOS High Sierra.
> On Linux I also debugged gdb to ensure that the thread names are still
> set correctly.
>
> gdb/ChangeLog
> 2019-12-10 Tom Tromey <tromey@adacore.com>
>
> PR build/25268:
> * gdbsupport/thread-pool.c (set_thread_name): New template
> function.
> (thread_pool::set_thread_count): Don't call pthread_setname_np.
> (thread_pool::thread_function): Call set_thread_name.
Did this ever go in?
If not, I think it looks reasonable.
Kevin
>>>>> "Kevin" == Kevin Buettner <kevinb@redhat.com> writes:
>> gdb/ChangeLog
>> 2019-12-10 Tom Tromey <tromey@adacore.com>
>>
>> PR build/25268:
>> * gdbsupport/thread-pool.c (set_thread_name): New template
>> function.
>> (thread_pool::set_thread_count): Don't call pthread_setname_np.
>> (thread_pool::thread_function): Call set_thread_name.
Kevin> Did this ever go in?
Kevin> If not, I think it looks reasonable.
Something like it did, and then there was another fix after that.
Tom
On Fri, 31 Jan 2020 15:43:29 +0100
Tom Tromey <tromey@adacore.com> wrote:
> >>>>> "Kevin" == Kevin Buettner <kevinb@redhat.com> writes:
>
> >> gdb/ChangeLog
> >> 2019-12-10 Tom Tromey <tromey@adacore.com>
> >>
> >> PR build/25268:
> >> * gdbsupport/thread-pool.c (set_thread_name): New template
> >> function.
> >> (thread_pool::set_thread_count): Don't call pthread_setname_np.
> >> (thread_pool::thread_function): Call set_thread_name.
>
> Kevin> Did this ever go in?
>
> Kevin> If not, I think it looks reasonable.
>
> Something like it did, and then there was another fix after that.
Yeah, I saw that there was a second fix, but I didn't see the template
stuff, which I thought was pretty cool.
Kevin
On Fri, Jan 31, 2020 at 4:02 PM Kevin Buettner <kevinb@redhat.com> wrote:
>
> On Fri, 31 Jan 2020 15:43:29 +0100
> Tom Tromey <tromey@adacore.com> wrote:
>
> > >>>>> "Kevin" == Kevin Buettner <kevinb@redhat.com> writes:
> >
> > >> gdb/ChangeLog
> > >> 2019-12-10 Tom Tromey <tromey@adacore.com>
> > >>
> > >> PR build/25268:
> > >> * gdbsupport/thread-pool.c (set_thread_name): New template
> > >> function.
> > >> (thread_pool::set_thread_count): Don't call pthread_setname_np.
> > >> (thread_pool::thread_function): Call set_thread_name.
> >
> > Kevin> Did this ever go in?
> >
> > Kevin> If not, I think it looks reasonable.
> >
> > Something like it did, and then there was another fix after that.
>
> Yeah, I saw that there was a second fix, but I didn't see the template
> stuff, which I thought was pretty cool.
The ultimate solution used function overloads instead of templates,
which seems simpler.
Christian
@@ -36,8 +36,28 @@
#endif
#ifdef USE_PTHREAD_SETNAME_NP
+
#include <pthread.h>
-#endif
+
+/* Handle platform discrepancies in pthread_setname_np: macOS uses a
+ single-argument form, while Linux uses a two-argument form. This
+ wrapper template handles the difference. */
+
+template<typename R, typename A1, typename A2>
+void
+set_thread_name (R (*set_name) (A1, A2), const char *name)
+{
+ set_name (pthread_self (), name);
+}
+
+template<typename R, typename A1>
+void
+set_thread_name (R (*set_name) (A1), const char *name)
+{
+ set_name (name);
+}
+
+#endif /* USE_PTHREAD_SETNAME_NP */
namespace gdb
{
@@ -75,9 +95,6 @@ thread_pool::set_thread_count (size_t num_threads)
for (size_t i = m_thread_count; i < num_threads; ++i)
{
std::thread thread (&thread_pool::thread_function, this);
-#ifdef USE_PTHREAD_SETNAME_NP
- pthread_setname_np (thread.native_handle (), "gdb worker");
-#endif
thread.detach ();
}
}
@@ -115,6 +132,12 @@ thread_pool::post_task (std::function<void ()> func)
void
thread_pool::thread_function ()
{
+#ifdef USE_PTHREAD_SETNAME_NP
+ /* This must be done here, because on macOS one can only set the
+ name of the current thread. */
+ set_thread_name (pthread_setname_np, "gdb worker");
+#endif
+
/* Ensure that SIGSEGV is delivered to an alternate signal
stack. */
gdb::alternate_signal_stack signal_stack;