[gdb] Fix hang after ext sigkill Consider the test-case from this patch, compiled with pthread support: ... $ gcc src/gdb/testsuite/gdb.threads/hang-after-ext-sigkill.c -lpthread ... After running, the program sleeps: ... $ gdb a.out Reading symbols from a.out... (gdb) r 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 0x7ffff77fe700 (LWP 22604)] ... Until we interrupt it with a control-C: ... ^C Thread 1 "a.out" received signal SIGINT, Interrupt. 0x00007ffff78c50f0 in nanosleep () from /lib64/libc.so.6 (gdb) ... If we then kill the inferior using an external SIGKILL: ... (gdb) shell killall -s SIGKILL a.out ... 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: 2020-02-24 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: 2020-02-24 Tom de Vries PR gdb/25471 * gdb.threads/hang-after-ext-sigkill.c: New test. * gdb.threads/hang-after-ext-sigkill.exp: New file. * lib/gdb.exp (runto): Handle "Temporary breakpoint" string. --- gdb/testsuite/gdb.threads/hang-after-ext-sigkill.c | 43 +++++++++++ .../gdb.threads/hang-after-ext-sigkill.exp | 88 ++++++++++++++++++++++ gdb/testsuite/lib/gdb.exp | 2 +- gdb/thread.c | 12 ++- 4 files changed, 142 insertions(+), 3 deletions(-) diff --git a/gdb/testsuite/gdb.threads/hang-after-ext-sigkill.c b/gdb/testsuite/gdb.threads/hang-after-ext-sigkill.c new file mode 100644 index 0000000000..b93d6c644a --- /dev/null +++ b/gdb/testsuite/gdb.threads/hang-after-ext-sigkill.c @@ -0,0 +1,43 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2020 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#include +#include + +static void * +fun (void *dummy) +{ + int i; + + for (i = 0; i < 300; i++) + sleep (1); + + return NULL; +} + +int +main (void) +{ + int i; + pthread_t thread; + pthread_create (&thread, NULL, fun, NULL); + + for (i = 0; i < 300; i++) + sleep (1); + + return 0; +} diff --git a/gdb/testsuite/gdb.threads/hang-after-ext-sigkill.exp b/gdb/testsuite/gdb.threads/hang-after-ext-sigkill.exp new file mode 100644 index 0000000000..89b38b1f6c --- /dev/null +++ b/gdb/testsuite/gdb.threads/hang-after-ext-sigkill.exp @@ -0,0 +1,88 @@ +# Copyright (C) 2020 Free Software Foundation, Inc. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program 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 General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +# This test-case tests that continuing an inferior that has been killed +# using an external sigkill does not make gdb hang. + +standard_testfile + +if {[prepare_for_testing "failed to prepare" $testfile $srcfile \ + {pthreads}] == -1} { + return -1 +} + +set res [runto main no-message temporary] +if { $res != 1 } { + return -1 +} + +set pid -1 +gdb_test_multiple "info inferior 1" "get inferior pid" { + -re -wrap "process (\[0-9\]*).*" { + set pid $expect_out(1,string) + pass $gdb_test_name + } +} +if { $pid == -1 } { + return -1 +} + +gdb_test_multiple "continue" "" { + -re "Continuing" { + pass $gdb_test_name + } +} + +send_gdb "\003" + +gdb_test_multiple "" "get sigint" { + -re -wrap "received signal SIGINT, Interrupt\..*" { + pass $gdb_test_name + } +} + +gdb_test_no_output "shell kill -s SIGKILL $pid" "shell kill -s SIGKILL pid" + +set no_such_process_msg "Couldn't get registers: No such process\." +set killed_msg "Program terminated with signal SIGKILL, Killed\." +set no_longer_exists_msg "The program no longer exists\." +set not_being_run_msg "The program is not being run\." + +gdb_test_multiple "continue" "prompt after first continue" { + -re "Continuing\.\r\n\r\n$killed_msg\r\n$no_longer_exists_msg\r\n$gdb_prompt $" { + pass $gdb_test_name + # Regular output, bug condition was not triggered, we're done. + return -1 + } + -re "Continuing\.\r\n$no_such_process_msg\r\n$no_such_process_msg\r\n$gdb_prompt " { + pass $gdb_test_name + # Two times $no_such_process_msg. The bug condition was triggered, go + # check for it. + } + -re "Continuing\.\r\n$no_such_process_msg\r\n$gdb_prompt $" { + pass $gdb_test_name + # One time $no_such_process_msg. We're stuck here. The bug condition + # was not triggered, but we're not getting correct gdb behaviour either: + # every subsequent continue produces one no_such_process_msg. Give up. + return -1 + } +} + +gdb_test_multiple "" "messages" { + -re ".*$killed_msg.*$no_longer_exists_msg\r\n" { + pass $gdb_test_name + gdb_test "continue" $not_being_run_msg "second continue" + } +} diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp index e17ac0ef75..4cf2beca00 100644 --- a/gdb/testsuite/lib/gdb.exp +++ b/gdb/testsuite/lib/gdb.exp @@ -570,7 +570,7 @@ proc runto { function args } { } return 1 } - -re "Breakpoint \[0-9\]*, \[0-9xa-f\]* in .*$gdb_prompt $" { + -re "\[Bb\]reakpoint \[0-9\]*, \[0-9xa-f\]* in .*$gdb_prompt $" { if { $print_pass } { pass $test_name } diff --git a/gdb/thread.c b/gdb/thread.c index c6e3d356a5..d287bce45f 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 &ex) + { + m_selected_frame_id = null_frame_id; + m_selected_frame_level = -1; + } tp->incref (); m_thread = tp;