From patchwork Wed Aug 16 17:41:43 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Buettner X-Patchwork-Id: 22161 Received: (qmail 94340 invoked by alias); 16 Aug 2017 17:41:50 -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 94310 invoked by uid 89); 16 Aug 2017 17:41:47 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No 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, RP_MATCHES_RCVD, SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=occasionally X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 16 Aug 2017 17:41:46 +0000 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D2292C062EB3 for ; Wed, 16 Aug 2017 17:41:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com D2292C062EB3 Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=kevinb@redhat.com Received: from pinnacle.lan (ovpn-117-126.phx2.redhat.com [10.3.117.126]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AEDF668D51 for ; Wed, 16 Aug 2017 17:41:44 +0000 (UTC) Date: Wed, 16 Aug 2017 10:41:43 -0700 From: Kevin Buettner To: gdb-patches@sourceware.org Subject: Re: [PATCH v4 5/7] Add thread_db_notice_clone to gdbserver Message-ID: <20170816104143.0af5d91a@pinnacle.lan> In-Reply-To: <20170816092542.6d2deb00@pinnacle.lan> References: <20170816092542.6d2deb00@pinnacle.lan> MIME-Version: 1.0 X-IsSubscribed: yes While working on a patch for fetching a thread handle in gdbserver, I ran into a circumstance in which tests in gdb.mi/mi-nsmoribund.exp would occasionally fail. Over a large enough number of runs, it would fail roughly 2% of the time. That thread handle patch caused find_one_thread() to be called on every stop. find_one_thread() calls td_ta_map_lwp2thr() which, in turn, can cause ps_get_thread_area() to be called. ps_get_thread_area() makes a call to ptrace() for getting the thread area address. If this should happen when the thread is not stopped, the call to ptrace will return error which in turn propogates back to find_one_thread(). find_one_thread() calls error() in this instance which causes the program to die. This patch causes find_one_thread() to be called upon reciept of a clone event. Since the clone is stopped, the circumstances described above cannot occur. gdb/gdbserver/ChangeLog: * linux-low.c (handle_extended_wait): Call thread_db_notice_clone(). * linux-low.h (thread_db_notice_clone): Declare. * thread-db.c (thread_db_notice_clone): New function. --- gdb/gdbserver/linux-low.c | 2 ++ gdb/gdbserver/linux-low.h | 6 ++++++ gdb/gdbserver/thread-db.c | 16 ++++++++++++++++ 3 files changed, 24 insertions(+) diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c index fd46d85..2b43f51 100644 --- a/gdb/gdbserver/linux-low.c +++ b/gdb/gdbserver/linux-low.c @@ -656,6 +656,8 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat) new_lwp->status_pending = status; } + thread_db_notice_clone (get_thread_process (event_thr), ptid); + /* Don't report the event. */ return 1; } diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h index 2bf7e7c..3d5cb66 100644 --- a/gdb/gdbserver/linux-low.h +++ b/gdb/gdbserver/linux-low.h @@ -410,4 +410,10 @@ int thread_db_get_tls_address (struct thread_info *thread, CORE_ADDR offset, CORE_ADDR load_module, CORE_ADDR *address); int thread_db_look_up_one_symbol (const char *name, CORE_ADDR *addrp); +/* Called from linux-low.c when a clone event is detected. Upon entry, + both the clone and the parent should be stopped. This function does + whatever is required have the clone under thread_db's control. */ + +void thread_db_notice_clone (struct process_info *proc, ptid_t lwp); + extern int have_ptrace_getregset; diff --git a/gdb/gdbserver/thread-db.c b/gdb/gdbserver/thread-db.c index 1ffb79d..b4a5188 100644 --- a/gdb/gdbserver/thread-db.c +++ b/gdb/gdbserver/thread-db.c @@ -864,3 +864,19 @@ thread_db_handle_monitor_command (char *mon) /* Tell server.c to perform default processing. */ return 0; } + +/* See linux-low.h. */ + +void +thread_db_notice_clone (struct process_info *proc, ptid_t ptid) +{ + struct thread_db *thread_db = proc->priv->thread_db; + + /* If the thread layer isn't initialized, return. It may just + be that the program uses clone, but does not use libthread_db. */ + if (thread_db == NULL || !thread_db->all_symbols_looked_up) + return; + + if (!find_one_thread (ptid)) + warning ("Cannot find thread after clone.\n"); +}