From 237b37f6cce1b85b3eb766fdac7f5835d90d16c09bf52f547a902ae1922426fb Mon Sep 17 00:00:00 2001 From: Michael Matz Date: Wed, 19 Feb 2020 16:18:21 +0000 Subject: [PATCH] Accepting request 770204 from home:tomdevries:branches:devel:gcc-gdb-hang-with-warning - Fix hang after SIGKILL [swo#25478]. * gdb-threads-fix-hang-in-stop_all_threads-after-killing-inferior.patch OBS-URL: https://build.opensuse.org/request/show/770204 OBS-URL: https://build.opensuse.org/package/show/devel:gcc/gdb?expand=0&rev=243 --- ...p_all_threads-after-killing-inferior.patch | 140 ++++++++++++++++++ gdb.changes | 6 + gdb.spec | 6 +- 3 files changed, 151 insertions(+), 1 deletion(-) create mode 100644 gdb-threads-fix-hang-in-stop_all_threads-after-killing-inferior.patch diff --git a/gdb-threads-fix-hang-in-stop_all_threads-after-killing-inferior.patch b/gdb-threads-fix-hang-in-stop_all_threads-after-killing-inferior.patch new file mode 100644 index 0000000..09c406b --- /dev/null +++ b/gdb-threads-fix-hang-in-stop_all_threads-after-killing-inferior.patch @@ -0,0 +1,140 @@ +[gdb/threads] Fix hang in stop_all_threads after killing inferior + +Consider a two-threaded testcase a.out, sleeping in both its threads: +... +$ gdb -ex r --args a.out +Reading symbols from a.out... +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 31268)] +... + +Typing ^C causes stop_all_threads to be executed, and if an external SIGKILL +(such as caused by killall -9 a.out) arrives at the start of stop_all_threads, +gdb hangs in stop_all_threads after giving this warning: +... +warning: unable to open /proc file '/proc/24938/status' +... + +Using "set debug infrun 1" we can see in more detail where we hang: +... +infrun: stop_all_threads +infrun: stop_all_threads, pass=0, iterations=0 +infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing +infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, need stop +infrun: target_wait (-1.0.0, status) = +infrun: 10264.10268.0 [Thread 0x7ffff77fe700 (LWP 10268)], +infrun: status->kind = signalled, signal = GDB_SIGNAL_KILL +infrun: stop_all_threads status->kind = signalled, signal = GDB_SIGNAL_KILL \ + Thread 0x7ffff77fe700 (LWP 10268) +infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing +infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping +warning: unable to open /proc file '/proc/10264/status' +infrun: target_wait (-1.0.0, status) = +infrun: -1.0.0 [process -1], +infrun: status->kind = no-resumed +infrun: infrun_async(0) +infrun: stop_all_threads status->kind = no-resumed process -1 +infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing +infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping +infrun: stop_all_threads status->kind = no-resumed process -1 +infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing +infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping +infrun: stop_all_threads status->kind = no-resumed process -1 +infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing +infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping + +...... + +So, we're hanging in the 'while (1)' loop in stop_all_threads as follows: +- thread t is tested, and both t->executing and t->stop_requested are found + to be 1 (noted with 'executing, already stopping') +- consequently need_wait is set 1 +- consequently wait_one is executed +- wait_one returns a TARGET_WAITKIND_NO_RESUMED event, which is handled by + continuing at the start of the loop + +The loop actually starts with update_thread_list (), but that doesn't seem +to change the state of the threads. + +Fix the hang by: +- detecting the first sign of trouble: the TARGET_WAITKIND_SIGNALLED event + with signal GDB_SIGNAL_KILL, +- making that event pending again, +- making sure the corresponding thread will not set need_wait again + (by setting t->executing == 0) +- making sure that the corresponding thread keeps t->resumed == 1 in the + the all_non_exited_threads loop + +This results in the ^C being handled without showing the user that the +test-case was killed: +... +^C +Thread 1 received signal SIGINT, Interrupt. +0x00007ffff78c50f0 in nanosleep () from /lib64/libc.so.6 +(gdb) +... + +But a subsequent continue does show that: +... +(gdb) c +Continuing. + +Program terminated with signal SIGKILL, Killed. +The program no longer exists. +(gdb) +.... + +Build and reg-tested on x86_64-linux. + +gdb/ChangeLog: + +2020-01-29 Tom de Vries + + PR threads/25478 + * infrun.c (stop_all_threads): Detecting event + TARGET_WAITKIND_SIGNALLED with signal GDB_SIGNAL_KILL, make event + pending again, set t->executing to 0 and keep t->resumed set to 1. + +Change-Id: Ibe1f29251fe2ff1c1991f041babbe18373c113b1 + +--- + gdb/infrun.c | 17 +++++++++++++++-- + 1 file changed, 15 insertions(+), 2 deletions(-) + +diff --git a/gdb/infrun.c b/gdb/infrun.c +index 9d20036fcf..16e9e136c0 100644 +--- a/gdb/infrun.c ++++ b/gdb/infrun.c +@@ -4344,7 +4344,12 @@ stop_all_threads (void) + + /* The thread may be not executing, but still be + resumed with a pending status to process. */ +- t->resumed = 0; ++ if (t->suspend.waitstatus.kind == TARGET_WAITKIND_SIGNALLED ++ && t->suspend.waitstatus.value.sig == GDB_SIGNAL_KILL ++ && t->suspend.waitstatus_pending_p) ++ ; ++ else ++ t->resumed = 0; + } + } + +@@ -4359,7 +4364,15 @@ stop_all_threads (void) + + event_ptid = wait_one (&ws); + +- if (ws.kind == TARGET_WAITKIND_NO_RESUMED) ++ if (ws.kind == TARGET_WAITKIND_SIGNALLED ++ && ws.value.sig == GDB_SIGNAL_KILL) ++ { ++ thread_info *t = find_thread_ptid (event_ptid); ++ save_waitstatus (t, &ws); ++ t->resumed = 1; ++ t->executing = 0; ++ } ++ else if (ws.kind == TARGET_WAITKIND_NO_RESUMED) + { + /* All resumed threads exited. */ + } diff --git a/gdb.changes b/gdb.changes index d62973d..578fa3f 100644 --- a/gdb.changes +++ b/gdb.changes @@ -1,3 +1,9 @@ +------------------------------------------------------------------- +Tue Feb 4 19:56:55 UTC 2020 - Tom de Vries + +- Fix hang after SIGKILL [swo#25478]. + * gdb-threads-fix-hang-in-stop_all_threads-after-killing-inferior.patch + ------------------------------------------------------------------- Fri Jan 17 15:43:46 UTC 2020 - matz@suse.com diff --git a/gdb.spec b/gdb.spec index 3758970..5c75abf 100644 --- a/gdb.spec +++ b/gdb.spec @@ -13,7 +13,7 @@ # license that conforms to the Open Source Definition (Version 1.9) # published by the Open Source Initiative. -# Please submit bugfixes or comments via http://bugs.opensuse.org/ +# Please submit bugfixes or comments via https://bugs.opensuse.org/ # @@ -258,6 +258,9 @@ Patch2500: gdb-symtab-prefer-var-def-over-decl.patch # Proposed patch for PR gdb/24956 Patch2501: gdb-only-force-interp_console-ui_out-for-breakpoint-commands-in-mi-mode.patch +# Proposed patch for PR threads/25478 +Patch2502: gdb-threads-fix-hang-in-stop_all_threads-after-killing-inferior.patch + # Testsuite patches Patch2600: gdb-testsuite-8.3-kfail-xfail-unsupported.patch @@ -610,6 +613,7 @@ find -name "*.info*"|xargs rm -f %patch2500 -p1 %patch2501 -p1 +%patch2502 -p1 %patch2600 -p1