From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f42.google.com (mail-wr1-f42.google.com [209.85.221.42]) by sourceware.org (Postfix) with ESMTPS id 5C558388DF39 for ; Wed, 13 Jul 2022 22:25:09 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 5C558388DF39 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-wr1-f42.google.com with SMTP id b26so47033wrc.2 for ; Wed, 13 Jul 2022 15:25:09 -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=K8HHXo4QvUa1Iq9Xsa62r+vZv1LkEWyWh6F1VyWUi38=; b=lQe6FJeZgNHm/Y6W8EdvUiNu+jS+d+tntYikxeS30jOtWmzBOReNhf7oxj8aw5L/1b 3sgeKTUBvD3zTvR7cGdikE0fpoTVTWksbSsS2SMjnq73zllunyJzu3LwQ78zWkcL9911 pPE2jirws3v/hQ6zncifCUBnzYY16Q2gIzsScLIQtgSIoDG8/oTGZEBEXlp+BqyxqfMI P3IjyN8pAtdJO9+UeVMcfZQaJIezyp9AHzD7IF4HEVtm2P07gUis/08+K/BxVrMY+gEp vnD673kyqxdg0BeFxn1/+HlYBju/riAqkYDUv7rPlcHsh4A10mJQhFfUSsiOOd0PI+0q pIfw== X-Gm-Message-State: AJIora9N6qZ2keoIVOg4EhQupQbMpJVEN60e+ZSw1xX1A5aTmOguTi8g uuIseb8gDbzX5aMfLrjN20UHmXg+dD8= X-Google-Smtp-Source: AGRyM1uHQSp4zxDpBhgDyVndMw3ab/FNFdrkLVKNh3z9idOLBYQWFLdjQaqxn5pwoCMK7HavmTe45Q== X-Received: by 2002:a05:6000:114e:b0:21d:6cd1:695d with SMTP id d14-20020a056000114e00b0021d6cd1695dmr5461175wrx.474.1657751108433; Wed, 13 Jul 2022 15:25:08 -0700 (PDT) Received: from localhost ([2001:8a0:f924:2600:209d:85e2:409e:8726]) by smtp.gmail.com with ESMTPSA id m23-20020a05600c3b1700b003a2e278510csm3667954wms.15.2022.07.13.15.25.07 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Jul 2022 15:25:07 -0700 (PDT) From: Pedro Alves To: gdb-patches@sourceware.org Subject: [PATCH v2 15/29] Introduce GDB_TO_EXIT thread option, fix step-over-thread-exit Date: Wed, 13 Jul 2022 23:24:19 +0100 Message-Id: <20220713222433.374898-16-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, 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 22:25:11 -0000 When stepping over a breakpoint with displaced stepping, GDB needs to be informed if the stepped thread exits, otherwise the displaced stepping buffer that was allocated to that thread leaks, and this can result in deadlock, with other threads waiting for their turn to displaced step, but their turn never comes. Similarly, when stepping over a breakpoint in line, GDB also needs to be informed if the stepped thread exits, so that is can clear the step over state and re-resume threads. This commit makes it possible for GDB to ask the target to report thread exit events for a given thread, using the new "thread options" mechanism introduced by a previous patch. This only adds the core bits. Following patches in the series will teach the Linux backends (native & gdbserver) to handle the GDB_TO_EXIT option, and then a later patch will make use of these thread exit events to clean up displaced stepping and inline stepping state properly. Change-Id: I96b719fdf7fee94709e98bb3a90751d8134f3a38 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338 --- gdb/infrun.c | 14 +++++++++----- gdb/remote.c | 9 +++++++++ gdb/target/target.h | 4 ++++ 3 files changed, 22 insertions(+), 5 deletions(-) diff --git a/gdb/infrun.c b/gdb/infrun.c index f3eea44375e..bc4accc0fd3 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -2376,24 +2376,28 @@ do_target_resume (ptid_t resume_ptid, bool step, enum gdb_signal sig) else target_pass_signals (signal_pass); - /* Request that the target report thread-{created,cloned} events in - the following situations: + /* Request that the target report thread-{created,cloned,exited} + events in the following situations: - If we are performing an in-line step-over-breakpoint, then we will remove a breakpoint from the target and only run the current thread. We don't want any new thread (spawned by the - step) to start running, as it might miss the breakpoint. + step) to start running, as it might miss the breakpoint. We + need to clear the step-over state if the stepped thread exits, + so we also enable thread-exit events. - If we are stepping over a breakpoint out of line (displaced stepping) then we won't remove a breakpoint from the target, but, if the step spawns a new clone thread, then we will need to fixup the $pc address in the clone child too, so we need it - to start stopped. + to start stopped. We need to release the displaced stepping + buffer if the stepped thread exits, so we also enable + thread-exit events. */ if (step_over_info_valid_p () || displaced_step_in_progress_thread (tp)) { - gdb_thread_options options = GDB_TO_CLONE; + gdb_thread_options options = GDB_TO_CLONE | GDB_TO_EXIT; if (target_supports_set_thread_options (options)) tp->set_thread_options (options); else diff --git a/gdb/remote.c b/gdb/remote.c index 090ea47aa38..4def89a57f8 100644 --- a/gdb/remote.c +++ b/gdb/remote.c @@ -4000,6 +4000,15 @@ remote_target::update_thread_list () if (has_single_non_exited_thread (tp->inf)) continue; + /* Do not remove the thread if we've requested to be + notified of its exit. For example, the thread may be + displaced stepping, infrun will need to handle the + exit event, and displaced stepping info is recorded + in the thread object. If we deleted the thread now, + we'd lose that info. */ + if ((tp->thread_options () & GDB_TO_EXIT) != 0) + continue; + /* Not found. */ delete_thread (tp); } diff --git a/gdb/target/target.h b/gdb/target/target.h index cba98114b5d..571d90cf7c0 100644 --- a/gdb/target/target.h +++ b/gdb/target/target.h @@ -31,6 +31,10 @@ enum gdb_thread_option : unsigned /* Tell the target to report TARGET_WAITKIND_THREAD_CLONED events for the thread. */ GDB_TO_CLONE = 1 << 0, + + /* Tell the target to report TARGET_WAITKIND_THREAD_EXIT events for + the thread. */ + GDB_TO_EXIT = 1 << 1, }; DEF_ENUM_FLAGS_TYPE (enum gdb_thread_option, gdb_thread_options); -- 2.36.0