From patchwork Tue Feb 28 18:18:41 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Baldwin X-Patchwork-Id: 65801 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id D6DF23850209 for ; Tue, 28 Feb 2023 18:19:26 +0000 (GMT) X-Original-To: gdb-patches@sourceware.org Delivered-To: gdb-patches@sourceware.org Received: from mail.baldwin.cx (bigwig.baldwin.cx [IPv6:2607:f138:0:13::2]) by sourceware.org (Postfix) with ESMTPS id DA0653858C50 for ; Tue, 28 Feb 2023 18:19:02 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org DA0653858C50 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=FreeBSD.org Authentication-Results: sourceware.org; spf=fail smtp.mailfrom=FreeBSD.org Received: from gimli.baldwin.net (c-98-35-126-114.hsd1.ca.comcast.net [98.35.126.114]) by mail.baldwin.cx (Postfix) with ESMTPSA id 6A5181A84E33 for ; Tue, 28 Feb 2023 13:18:57 -0500 (EST) From: John Baldwin To: gdb-patches@sourceware.org Subject: [PATCH 5/9] fbsd-nat: Defer any ineligible events reported by wait. Date: Tue, 28 Feb 2023 10:18:41 -0800 Message-Id: <20230228181845.99936-6-jhb@FreeBSD.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20230228181845.99936-1-jhb@FreeBSD.org> References: <20230228181845.99936-1-jhb@FreeBSD.org> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.4 (mail.baldwin.cx [0.0.0.0]); Tue, 28 Feb 2023 13:18:57 -0500 (EST) X-Virus-Scanned: clamav-milter 0.103.1 at mail.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-11.9 required=5.0 tests=BAYES_00, FORGED_SPF_HELO, GIT_PATCH_0, KAM_DMARC_STATUS, KHOP_HELO_FCRDNS, SPF_HELO_PASS, SPF_SOFTFAIL, TXREP 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: , Errors-To: gdb-patches-bounces+patchwork=sourceware.org@sourceware.org Sender: "Gdb-patches" If wait_1 finds an event for a thread or process that does not match the set of threads and processes previously resumed, defer the event. If the event is for a specific thread, suspend the thread and continue the associated process before waiting for another event. One specific example of such an event is if a thread is created while another thread in the same process hits a breakpoint. If the second thread's event is reported first, the target resume method does not yet "know" about the new thread and will not suspend it via PT_SUSPEND. When wait is called, it will probably return the event from the first thread before the result of the step from second thread. This is the case reported in PR 21497. --- gdb/fbsd-nat.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c index ca278b871ef..3f7278c6ea0 100644 --- a/gdb/fbsd-nat.c +++ b/gdb/fbsd-nat.c @@ -1514,7 +1514,39 @@ fbsd_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus, if (is_async_p ()) async_file_flush (); - wptid = wait_1 (ptid, ourstatus, target_options); + while (1) + { + wptid = wait_1 (ptid, ourstatus, target_options); + + /* If no event was found, just return. */ + if (ourstatus->kind () == TARGET_WAITKIND_IGNORE + || ourstatus->kind () == TARGET_WAITKIND_NO_RESUMED) + break; + + /* If an event is reported for a thread or process while + stepping some other thread, suspend the thread reporting the + event and defer the event until it can be reported to the + core. */ + if (!wptid.matches (resume_ptid)) + { + add_pending_event (wptid, *ourstatus); + fbsd_nat_debug_printf ("deferring event [%s], [%s]", + target_pid_to_str (wptid).c_str (), + ourstatus->to_string ().c_str ()); + if (wptid.pid () == resume_ptid.pid ()) + { + fbsd_nat_debug_printf ("suspending thread [%s]", + target_pid_to_str (wptid).c_str ()); + if (ptrace (PT_SUSPEND, wptid.lwp (), NULL, 0) == -1) + perror_with_name (("ptrace (PT_SUSPEND)")); + if (ptrace (PT_CONTINUE, wptid.pid (), (caddr_t) 1, 0) == -1) + perror_with_name (("ptrace (PT_CONTINUE)")); + } + continue; + } + + break; + } /* If we are in async mode and found an event, there may still be another event pending. Trigger the event pipe so that that the