| Message ID | 20191210214717.25680-1-tromey@adacore.com |
|---|---|
| State | New |
| Headers | show |
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
diff --git a/gdb/gdbsupport/thread-pool.c b/gdb/gdbsupport/thread-pool.c index d19ae02e3ef..8e24570ee96 100644 --- a/gdb/gdbsupport/thread-pool.c +++ b/gdb/gdbsupport/thread-pool.c @@ -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;