From patchwork Wed Jan 29 14:10:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Simon Marchi (Code Review)" X-Patchwork-Id: 37608 Received: (qmail 64280 invoked by alias); 29 Jan 2020 14:10:50 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 64103 invoked by uid 89); 29 Jan 2020 14:10:44 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3 autolearn=ham version=3.3.1 spammy=hanging, 24938, gdb_versions X-HELO: mx1.osci.io Received: from polly.osci.io (HELO mx1.osci.io) (8.43.85.229) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 29 Jan 2020 14:10:42 +0000 Received: by mx1.osci.io (Postfix, from userid 994) id D400320256; Wed, 29 Jan 2020 09:10:38 -0500 (EST) Received: from gnutoolchain-gerrit.osci.io (gnutoolchain-gerrit.osci.io [IPv6:2620:52:3:1:5054:ff:fe06:16ca]) by mx1.osci.io (Postfix) with ESMTP id AAFFB20179 for ; Wed, 29 Jan 2020 09:10:37 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by gnutoolchain-gerrit.osci.io (Postfix) with ESMTP id 794B320AF7 for ; Wed, 29 Jan 2020 09:10:37 -0500 (EST) X-Gerrit-PatchSet: 1 Date: Wed, 29 Jan 2020 09:10:37 -0500 From: "Tom de Vries (Code Review)" To: gdb-patches@sourceware.org Message-ID: Auto-Submitted: auto-generated X-Gerrit-MessageType: newchange Subject: [review] [gdb/threads] Fix hang in stop_all_threads after killing inferior X-Gerrit-Change-Id: Ibe1f29251fe2ff1c1991f041babbe18373c113b1 X-Gerrit-Change-Number: 759 X-Gerrit-ChangeURL: X-Gerrit-Commit: fe2db3d5c7f974e5387a3d2649e4c8f2d2a44bda References: Reply-To: tdevries@suse.de, gdb-patches@sourceware.org MIME-Version: 1.0 Content-Disposition: inline User-Agent: Gerrit/3.0.3-79-g83ff7f88f1 Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/759 ...................................................................... [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 causing 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 - 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, and breaking out of the loop. Build and reg-tested on x86_64-linux. gdb/ChangeLog: 2020-01-29 Tom de Vries PR threads/25478 * infrun.c (stop_all_threads): Return when detecting event TARGET_WAITKIND_SIGNALLED with signal GDB_SIGNAL_KILL. Change-Id: Ibe1f29251fe2ff1c1991f041babbe18373c113b1 --- M gdb/infrun.c 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/gdb/infrun.c b/gdb/infrun.c index 22de42c..e34ddc8 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -4772,7 +4772,10 @@ target_pid_to_str (event.ptid).c_str ()); } - if (event.ws.kind == TARGET_WAITKIND_NO_RESUMED + if (event.ws.kind == TARGET_WAITKIND_SIGNALLED + && event.ws.value.sig == GDB_SIGNAL_KILL) + goto done; + else if (event.ws.kind == TARGET_WAITKIND_NO_RESUMED || event.ws.kind == TARGET_WAITKIND_THREAD_EXITED || event.ws.kind == TARGET_WAITKIND_EXITED || event.ws.kind == TARGET_WAITKIND_SIGNALLED) @@ -4872,6 +4875,7 @@ } } + done: if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: stop_all_threads done\n"); }