From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm1-f48.google.com (mail-wm1-f48.google.com [209.85.128.48]) by sourceware.org (Postfix) with ESMTPS id B3409381559E for ; Wed, 13 Jul 2022 22:25:23 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org B3409381559E Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=palves.net Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wm1-f48.google.com with SMTP id c131-20020a1c3589000000b003a2cc290135so2048569wma.2 for ; Wed, 13 Jul 2022 15:25:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=nqQJFrlOKapWcXxT/C/QDJbP96RfzIyKVWtu49UxwMI=; b=X3iEMjsjoKLw69fFD6kXtqUE4/q3oenpQ6POPABaRg1XlJDcW/nTKaQWfMcfBMt8ZP pUMI0UHUG+K7zm98upDmSg/tuWWjccL2Tqq2012Was3teytlcTqYt28OEUePR3IRNF0Y hMRmgQW+/4OKCJ6f55Y7HUTbK+C8itiQ31GoIenb/OO9NoGq8nz2B/P4xn2SGYzOsY37 l03Kz3eGruk+EEr5IvUUlXq29rAGrMrCzEsS4kRnP9nZL3JwK0aNU7AgoUp7U/h8EoB6 TrJAYMEfSY6sRnfjkSZw9f1jHimb5a/L24FcTHptRjLUVDqVDFJ4FydAVHePdXXenpt1 WZnQ== X-Gm-Message-State: AJIora9zf6rNn+Dhh/NmbQzS9o4Rj+QUZrgBwqjNPk3uf78ilkYnicfs 2VdnPn8EI1v9TW+m9a4piohB229jsa8= X-Google-Smtp-Source: AGRyM1ttNN8AVkfuVXGi8rMFlCMIQRHkiE6WTvlKFOsLwFUaorUjanBGB6vFsmH8102lRqN7rEbBSw== X-Received: by 2002:a05:600c:22d2:b0:3a2:eb34:d1f1 with SMTP id 18-20020a05600c22d200b003a2eb34d1f1mr12172887wmg.193.1657751121602; Wed, 13 Jul 2022 15:25:21 -0700 (PDT) Received: from localhost ([2001:8a0:f924:2600:209d:85e2:409e:8726]) by smtp.gmail.com with ESMTPSA id az16-20020adfe190000000b0021d80f53324sm13112721wrb.7.2022.07.13.15.25.20 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Jul 2022 15:25:20 -0700 (PDT) From: Pedro Alves To: gdb-patches@sourceware.org Subject: [PATCH v2 21/29] Don't resume new threads if scheduler-locking is in effect Date: Wed, 13 Jul 2022 23:24:25 +0100 Message-Id: <20220713222433.374898-22-pedro@palves.net> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220713222433.374898-1-pedro@palves.net> References: <20220713222433.374898-1-pedro@palves.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-9.9 required=5.0 tests=BAYES_00, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, GIT_PATCH_0, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, KAM_SHORT, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 Jul 2022 22:25:26 -0000 If scheduler-locking is in effect, like e.g., with "set scheduler-locking on", and you step over a function that spawns a new thread, the new thread is allowed to run free, at least until some event is hit, at which point, whether the new thread is re-resumed depends on a number of seemingly random factors. E.g., if the target is all-stop, and the parent thread hits a breakpoint, and gdb decides the breakpoint isn't interesting to report to the user, then the parent thread is resumed, but the new thread is left stopped. I think that letting the new threads run with scheduler-locking enabled is a defect. This commit fixes that, making use of the new clone events on Linux, and of target_thread_events() on targets where new threads have no connection to the thread that spawned them. Testcase and documentation changes included. Change-Id: Ie12140138b37534b7fc1d904da34f0f174aa11ce --- gdb/NEWS | 7 +++ gdb/doc/gdb.texinfo | 4 +- gdb/infrun.c | 41 +++++++++--- .../gdb.threads/schedlock-new-thread.c | 46 ++++++++++++++ .../gdb.threads/schedlock-new-thread.exp | 63 +++++++++++++++++++ 5 files changed, 152 insertions(+), 9 deletions(-) create mode 100644 gdb/testsuite/gdb.threads/schedlock-new-thread.c create mode 100644 gdb/testsuite/gdb.threads/schedlock-new-thread.exp diff --git a/gdb/NEWS b/gdb/NEWS index 742f4fe47fb..f0f6990dc59 100644 --- a/gdb/NEWS +++ b/gdb/NEWS @@ -3,6 +3,13 @@ *** Changes since GDB 12 +* Scheduler-locking and new threads + + When scheduler-locking is in effect, only the current thread may run + when the inferior is resumed. However, previously, new threads + created by the resumed thread would still be able to run free. Now, + they are held stopped. + * "info breakpoints" now displays enabled breakpoint locations of disabled breakpoints as in the "y-" state. For example: diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 9a8b010476a..a15ef0ed0db 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -6947,7 +6947,9 @@ the following: There is no locking and any thread may run at any time. @item on -Only the current thread may run when the inferior is resumed. +Only the current thread may run when the inferior is resumed. New +threads created by the resumed thread are held stopped at their entry +point, before they execute any instruction. @item step Behaves like @code{on} when stepping, and @code{off} otherwise. diff --git a/gdb/infrun.c b/gdb/infrun.c index 50270ec4759..6df70e374b4 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -103,6 +103,8 @@ static bool start_step_over (void); static bool step_over_info_valid_p (void); +static bool schedlock_applies (struct thread_info *tp); + /* Asynchronous signal handler registered as event loop source for when we have pending events ready to be passed to the core. */ static struct async_event_handler *infrun_async_inferior_event_token; @@ -1823,7 +1825,13 @@ static void update_thread_events_after_step_over (thread_info *event_thread, const target_waitstatus &event_status) { - if (target_supports_set_thread_options (0)) + if (schedlock_applies (event_thread)) + { + /* If scheduler-locking applies, continue reporting + thread-created/thread-cloned events. */ + return; + } + else if (target_supports_set_thread_options (0)) { /* We can control per-thread options. Disable events for the event thread, unless the thread is gone. */ @@ -2395,9 +2403,14 @@ do_target_resume (ptid_t resume_ptid, bool step, enum gdb_signal sig) to start stopped. We need to release the displaced stepping buffer if the stepped thread exits, so we also enable thread-exit events. + + - If scheduler-locking applies, threads that the current thread + spawns should remain halted. It's not strictly necessary to + enable thread-exit events in this case, but it doesn't hurt. */ if (step_over_info_valid_p () - || displaced_step_in_progress_thread (tp)) + || displaced_step_in_progress_thread (tp) + || schedlock_applies (tp)) { gdb_thread_options options = GDB_TO_CLONE | GDB_TO_EXIT; if (target_supports_set_thread_options (options)) @@ -2405,6 +2418,13 @@ do_target_resume (ptid_t resume_ptid, bool step, enum gdb_signal sig) else target_thread_events (true); } + else + { + if (target_supports_set_thread_options (0)) + tp->set_thread_options (0); + else if (!displaced_step_in_progress_any_thread ()) + target_thread_events (false); + } /* If we're resuming more than one thread simultaneously, then any thread other than the leader is being set to run free. Clear any @@ -6007,16 +6027,21 @@ handle_inferior_event (struct execution_control_state *ecs) parent->set_running (false); /* If resuming the child, mark it running. */ - if (ecs->ws.kind () == TARGET_WAITKIND_THREAD_CLONED - || (follow_child || (!detach_fork && (non_stop || sched_multi)))) + if ((ecs->ws.kind () == TARGET_WAITKIND_THREAD_CLONED + && !schedlock_applies (ecs->event_thread)) + || (ecs->ws.kind () != TARGET_WAITKIND_THREAD_CLONED + && (follow_child + || (!detach_fork && (non_stop || sched_multi))))) child->set_running (true); /* In non-stop mode, also resume the other branch. */ if ((ecs->ws.kind () == TARGET_WAITKIND_THREAD_CLONED - && target_is_non_stop_p ()) - || (!detach_fork && (non_stop - || (sched_multi - && target_is_non_stop_p ())))) + && target_is_non_stop_p () + && !schedlock_applies (ecs->event_thread)) + || (ecs->ws.kind () != TARGET_WAITKIND_THREAD_CLONED + && (!detach_fork && (non_stop + || (sched_multi + && target_is_non_stop_p ()))))) { if (follow_child) switch_to_thread (parent); diff --git a/gdb/testsuite/gdb.threads/schedlock-new-thread.c b/gdb/testsuite/gdb.threads/schedlock-new-thread.c new file mode 100644 index 00000000000..67a2ef61a7b --- /dev/null +++ b/gdb/testsuite/gdb.threads/schedlock-new-thread.c @@ -0,0 +1,46 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2021-2022 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 +#include + +static void * +thread_func (void *arg) +{ + while (1) + sleep (1); +} + +int +main (void) +{ + pthread_t thread; + int ret; + + ret = pthread_create (&thread, NULL, thread_func, NULL); /* set break 1 here */ + assert (ret == 0); + + /* When testing with schedlock enabled, the new thread won't run, so + we can't join it, as that would hang forever. Instead, sleep for + a bit, enough that if the spawned thread is scheduled, it hits + the thread_func breakpoint before the main thread reaches the + "return 0" line below. */ + sleep (3); + + return 0; /* set break 2 here */ +} diff --git a/gdb/testsuite/gdb.threads/schedlock-new-thread.exp b/gdb/testsuite/gdb.threads/schedlock-new-thread.exp new file mode 100644 index 00000000000..8952cb7531c --- /dev/null +++ b/gdb/testsuite/gdb.threads/schedlock-new-thread.exp @@ -0,0 +1,63 @@ +# Copyright 2021-2022 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 . + +# Test continuing over a thread spawn with scheduler-locking on. + +standard_testfile .c + +set syscalls_src $srcdir/lib/my-syscalls.S + +if { [build_executable "failed to prepare" $testfile \ + [list $srcfile $syscalls_src] {debug pthreads}] == -1 } { + return +} + +proc test {non-stop schedlock} { + save_vars ::GDBFLAGS { + append ::GDBFLAGS " -ex \"set non-stop ${non-stop}\"" + clean_restart $::binfile + } + + set linenum1 [gdb_get_line_number "set break 1 here"] + + if { ![runto $::srcfile:$linenum1] } { + return + } + + delete_breakpoints + + set linenum2 [gdb_get_line_number "set break 2 here"] + gdb_breakpoint $linenum2 + + gdb_breakpoint "thread_func" + + gdb_test_no_output "set scheduler-locking $schedlock" + + if {$schedlock} { + gdb_test "continue" \ + "return 0.*set break 2 here .*" \ + "continue does not stop in new thread" + } else { + gdb_test "continue" \ + "thread_func .*" \ + "continue stops in new thread" + } +} + +foreach_with_prefix non-stop {off on} { + foreach_with_prefix schedlock {off on} { + test ${non-stop} ${schedlock} + } +} -- 2.36.0