From 8a06aea71e0aa9099d0ca593dbb58f6e056af4ff Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Tue, 7 Apr 2015 15:47:22 +0100 Subject: update thread list, delete exited threads On GNU/Linux, if the running kernel supports clone events, then linux-thread-db.c defers thread listing to the target beneath: static void thread_db_update_thread_list (struct target_ops *ops) { ... if (target_has_execution && !thread_db_use_events ()) ops->beneath->to_update_thread_list (ops->beneath); else thread_db_update_thread_list_td_ta_thr_iter (ops); ... } However, when live debugging, the target beneath, linux-nat.c, does not implement the to_update_thread_list method. The result is that if a thread is marked exited (because it can't be deleted right now, e.g., it was the selected thread), then it won't ever be deleted, until the process exits or is killed/detached. A similar thing happens with the remote.c target. Because its target_update_thread_list implementation skips exited threads when it walks the current thread list looking for threads that no longer exits on the target side, using ALL_NON_EXITED_THREADS_SAFE, stale exited threads are never deleted. This is not a big deal -- I can't think of any way this might be user visible, other than gdb's memory growing a tiny bit whenever a thread gets stuck in exited state. Still, might as well clean things up properly. All other targets use prune_threads, so are unaffected. The fix adds a ALL_THREADS_SAFE macro, that like ALL_NON_EXITED_THREADS_SAFE, walks the thread list and allows deleting the iterated thread, and uses that in places that are walking the thread list in order to delete threads. Actually, after converting linux-nat.c and remote.c to use this, we find the only other user of ALL_NON_EXITED_THREADS_SAFE is also walking the list to delete threads. So we convert that too, and end up deleting ALL_NON_EXITED_THREADS_SAFE. Tested on x86_64 Fedora 20, native and gdbserver. gdb/ChangeLog 2015-04-07 Pedro Alves * gdbthread.h (ALL_NON_EXITED_THREADS_SAFE): Rename to ... (ALL_THREADS_SAFE): ... this, and don't skip exited threads. (delete_exited_threads): New declaration. * infrun.c (follow_exec): Use ALL_THREADS_SAFE. * linux-nat.c (linux_nat_update_thread_list): New function. (linux_nat_add_target): Install it. * remote.c (remote_update_thread_list): Use ALL_THREADS_SAFE. * thread.c (prune_threads): Use ALL_THREADS_SAFE. (delete_exited_threads): New function. --- gdb/linux-nat.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'gdb/linux-nat.c') diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c index 04707dc..6c198cf 100644 --- a/gdb/linux-nat.c +++ b/gdb/linux-nat.c @@ -4030,6 +4030,23 @@ linux_nat_thread_alive (struct target_ops *ops, ptid_t ptid) return linux_thread_alive (ptid); } +/* Implement the to_update_thread_list target method for this + target. */ + +static void +linux_nat_update_thread_list (struct target_ops *ops) +{ + if (linux_supports_traceclone ()) + { + /* With support for clone events, we add/delete threads from the + list as clone/exit events are processed, so just try deleting + exited threads still in the thread list. */ + delete_exited_threads (); + } + else + prune_threads (); +} + static char * linux_nat_pid_to_str (struct target_ops *ops, ptid_t ptid) { @@ -4854,6 +4871,7 @@ linux_nat_add_target (struct target_ops *t) t->to_kill = linux_nat_kill; t->to_mourn_inferior = linux_nat_mourn_inferior; t->to_thread_alive = linux_nat_thread_alive; + t->to_update_thread_list = linux_nat_update_thread_list; t->to_pid_to_str = linux_nat_pid_to_str; t->to_thread_name = linux_nat_thread_name; t->to_has_thread_control = tc_schedlock; -- cgit v1.1