From 4778a5f87d253399083565b4919816f541ebe414 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Tue, 21 Apr 2020 15:45:57 +0200 Subject: [gdb] Fix hang after ext sigkill Consider the test-case from this patch, compiled with pthread support: ... $ gcc gdb/testsuite/gdb.threads/killed-outside.c -lpthread -g ... After running to all_started, we can print pid: ... $ gdb a.out -ex "b all_started" -ex run -ex "delete 1" -ex "p pid" ... Reading symbols from a.out... Breakpoint 1 at 0x40072b: file killed-outside.c, line 29. Starting program: /data/gdb_versions/devel/a.out [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib64/libthread_db.so.1". [New Thread 0x7ffff77fc700 (LWP 3155)] Thread 1 "a.out" hit Breakpoint 1, all_started () at killed-outside.c:29 29 } $1 = 3151 (gdb) ... If we then kill the inferior using an external SIGKILL: ... (gdb) shell kill -9 3151 ... and subsequently continue: ... (gdb) c Continuing. Couldn't get registers: No such process. Couldn't get registers: No such process. (gdb) Couldn't get registers: No such process. (gdb) Couldn't get registers: No such process. (gdb) Couldn't get registers: No such process. ... gdb hangs repeating the same warning. Typing control-C no longer helps, and we have to kill gdb. This is a regression since commit 873657b9e8 "Preserve selected thread in all-stop w/ background execution". The commit adds a scoped_restore_current_thread typed variable restore_thread to fetch_inferior_event, and the hang is caused by the constructor throwing an exception. Fix this by catching the exception in the constructor. Build and reg-tested on x86_64-linux. gdb/ChangeLog: 2020-04-21 Tom de Vries PR gdb/25471 * thread.c (scoped_restore_current_thread::scoped_restore_current_thread): Catch exception in get_frame_id. gdb/testsuite/ChangeLog: 2020-04-21 Tom de Vries PR gdb/25471 * gdb.threads/killed-outside.c: New test. * gdb.threads/killed-outside.exp: New file. --- gdb/thread.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'gdb/thread.c') diff --git a/gdb/thread.c b/gdb/thread.c index c6e3d35..03805bd 100644 --- a/gdb/thread.c +++ b/gdb/thread.c @@ -1488,8 +1488,16 @@ scoped_restore_current_thread::scoped_restore_current_thread () else frame = NULL; - m_selected_frame_id = get_frame_id (frame); - m_selected_frame_level = frame_relative_level (frame); + try + { + m_selected_frame_id = get_frame_id (frame); + m_selected_frame_level = frame_relative_level (frame); + } + catch (const gdb_exception_error &ex) + { + m_selected_frame_id = null_frame_id; + m_selected_frame_level = -1; + } tp->incref (); m_thread = tp; -- cgit v1.1