237b37f6cc
- 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
141 lines
4.7 KiB
Diff
141 lines
4.7 KiB
Diff
[gdb/threads] Fix hang in stop_all_threads after killing inferior
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Consider a two-threaded testcase a.out, sleeping in both its threads:
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...
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$ gdb -ex r --args a.out
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Reading symbols from a.out...
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Starting program: /data/gdb_versions/devel/a.out
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[Thread debugging using libthread_db enabled]
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Using host libthread_db library "/lib64/libthread_db.so.1".
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[New Thread 0x7ffff77fe700 (LWP 31268)]
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...
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Typing ^C causes stop_all_threads to be executed, and if an external SIGKILL
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(such as caused by killall -9 a.out) arrives at the start of stop_all_threads,
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gdb hangs in stop_all_threads after giving this warning:
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...
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warning: unable to open /proc file '/proc/24938/status'
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...
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Using "set debug infrun 1" we can see in more detail where we hang:
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...
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infrun: stop_all_threads
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infrun: stop_all_threads, pass=0, iterations=0
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infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing
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infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, need stop
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infrun: target_wait (-1.0.0, status) =
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infrun: 10264.10268.0 [Thread 0x7ffff77fe700 (LWP 10268)],
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infrun: status->kind = signalled, signal = GDB_SIGNAL_KILL
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infrun: stop_all_threads status->kind = signalled, signal = GDB_SIGNAL_KILL \
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Thread 0x7ffff77fe700 (LWP 10268)
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infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing
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infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping
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warning: unable to open /proc file '/proc/10264/status'
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infrun: target_wait (-1.0.0, status) =
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infrun: -1.0.0 [process -1],
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infrun: status->kind = no-resumed
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infrun: infrun_async(0)
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infrun: stop_all_threads status->kind = no-resumed process -1
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infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing
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infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping
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infrun: stop_all_threads status->kind = no-resumed process -1
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infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing
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infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping
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infrun: stop_all_threads status->kind = no-resumed process -1
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infrun: Thread 0x7ffff7fa6740 (LWP 10264) not executing
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infrun: Thread 0x7ffff77fe700 (LWP 10268) executing, already stopping
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<repeat>
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......
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So, we're hanging in the 'while (1)' loop in stop_all_threads as follows:
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- thread t is tested, and both t->executing and t->stop_requested are found
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to be 1 (noted with 'executing, already stopping')
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- consequently need_wait is set 1
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- consequently wait_one is executed
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- wait_one returns a TARGET_WAITKIND_NO_RESUMED event, which is handled by
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continuing at the start of the loop
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The loop actually starts with update_thread_list (), but that doesn't seem
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to change the state of the threads.
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Fix the hang by:
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- detecting the first sign of trouble: the TARGET_WAITKIND_SIGNALLED event
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with signal GDB_SIGNAL_KILL,
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- making that event pending again,
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- making sure the corresponding thread will not set need_wait again
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(by setting t->executing == 0)
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- making sure that the corresponding thread keeps t->resumed == 1 in the
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the all_non_exited_threads loop
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This results in the ^C being handled without showing the user that the
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test-case was killed:
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...
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^C
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Thread 1 received signal SIGINT, Interrupt.
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0x00007ffff78c50f0 in nanosleep () from /lib64/libc.so.6
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(gdb)
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...
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But a subsequent continue does show that:
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...
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(gdb) c
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Continuing.
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Program terminated with signal SIGKILL, Killed.
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The program no longer exists.
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(gdb)
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....
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Build and reg-tested on x86_64-linux.
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gdb/ChangeLog:
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2020-01-29 Tom de Vries <tdevries@suse.de>
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PR threads/25478
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* infrun.c (stop_all_threads): Detecting event
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TARGET_WAITKIND_SIGNALLED with signal GDB_SIGNAL_KILL, make event
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pending again, set t->executing to 0 and keep t->resumed set to 1.
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Change-Id: Ibe1f29251fe2ff1c1991f041babbe18373c113b1
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---
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gdb/infrun.c | 17 +++++++++++++++--
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1 file changed, 15 insertions(+), 2 deletions(-)
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diff --git a/gdb/infrun.c b/gdb/infrun.c
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index 9d20036fcf..16e9e136c0 100644
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--- a/gdb/infrun.c
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+++ b/gdb/infrun.c
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@@ -4344,7 +4344,12 @@ stop_all_threads (void)
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/* The thread may be not executing, but still be
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resumed with a pending status to process. */
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- t->resumed = 0;
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+ if (t->suspend.waitstatus.kind == TARGET_WAITKIND_SIGNALLED
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+ && t->suspend.waitstatus.value.sig == GDB_SIGNAL_KILL
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+ && t->suspend.waitstatus_pending_p)
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+ ;
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+ else
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+ t->resumed = 0;
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}
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}
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@@ -4359,7 +4364,15 @@ stop_all_threads (void)
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event_ptid = wait_one (&ws);
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- if (ws.kind == TARGET_WAITKIND_NO_RESUMED)
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+ if (ws.kind == TARGET_WAITKIND_SIGNALLED
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+ && ws.value.sig == GDB_SIGNAL_KILL)
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+ {
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+ thread_info *t = find_thread_ptid (event_ptid);
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+ save_waitstatus (t, &ws);
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+ t->resumed = 1;
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+ t->executing = 0;
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+ }
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+ else if (ws.kind == TARGET_WAITKIND_NO_RESUMED)
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{
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/* All resumed threads exited. */
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}
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