From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22047 invoked by alias); 4 Jun 2004 19:22:48 -0000 Mailing-List: contact gdb-patches-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sources.redhat.com Received: (qmail 21997 invoked from network); 4 Jun 2004 19:22:45 -0000 Received: from unknown (HELO mx1.redhat.com) (66.187.233.31) by sourceware.org with SMTP; 4 Jun 2004 19:22:45 -0000 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx1.redhat.com (8.12.10/8.12.10) with ESMTP id i54JMdi5016228 for ; Fri, 4 Jun 2004 15:22:39 -0400 Received: from potter.sfbay.redhat.com (potter.sfbay.redhat.com [172.16.27.15]) by int-mx2.corp.redhat.com (8.11.6/8.11.6) with ESMTP id i54JMWw30437; Fri, 4 Jun 2004 15:22:33 -0400 Received: from redhat.com (dhcp-172-16-25-160.sfbay.redhat.com [172.16.25.160]) by potter.sfbay.redhat.com (8.11.6/8.11.6) with ESMTP id i54JMVP23272; Fri, 4 Jun 2004 12:22:32 -0700 Message-ID: <40C0CBF7.1070300@redhat.com> Date: Fri, 04 Jun 2004 19:22:00 -0000 From: Michael Snyder Organization: Red Hat, Inc. User-Agent: Mozilla/5.0 (X11; U; Linux i686; es-ES; rv:1.4.2) Gecko/20040301 MIME-Version: 1.0 To: Jeff Johnston CC: gdb-patches@sources.redhat.com, drow@false.org Subject: Re: [RFA]: Dead Thread Patch References: <40C0BCB5.8090407@redhat.com> In-Reply-To: <40C0BCB5.8090407@redhat.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2004-06/txt/msg00081.txt.bz2 Jeff Johnston wrote: > The attached patch handles a problem I have run into while working on > threaded watchpoints. What happens is that a thread may die and we have > other events occurring at the same time (e.g. watchpoints). If the > thread_alive() function gets run by a gdb interface in the meantime, the > thread will be removed on the thread list. What later happens is that > we get the death event to handle and we see a tid that is not found on > the thread list. We think we have discovered a new thread and add it. > This causes all kinds of problems in the future if we attempt to get > registers or switch to the dead thread, etc. > > My patch attempts to recognize the situation and avoid any processing of > the dead thread event. I have tested this with the testsuite on i686 to > verify there are no regressions. > > Daniel, I cc'd you in case this fixes some of the occasional random > thread errors you were seeing and couldn't explain. > > Ok to commit? Looks good to me (s/prior/previously/) > > -- Jeff J. > > 2004-06-04 Jeff Johnston > > * infrun.c (handle_inferior_event): Don't treat an invalid ptid > as a new thread event. > * thread_db.c (thread_get_info_callback): If the thread is a > zombie, return TD_THR_ZOMBIE. > * (thread_from_lwp): If thread_get_info_callback returns > TD_THR_ZOMBIE, check if the thread is still on the thread list > and return a -1 ptid if not found. > (thread_db_wait): If thread_from_lwp returns a -1 ptid, then > change the status to TARGET_WAITKIND_SPURIOUS. > > > ------------------------------------------------------------------------ > > Index: infrun.c > =================================================================== > RCS file: /cvs/src/src/gdb/infrun.c,v > retrieving revision 1.163 > diff -u -p -r1.163 infrun.c > --- infrun.c 14 May 2004 18:45:42 -0000 1.163 > +++ infrun.c 4 Jun 2004 18:13:53 -0000 > @@ -1332,6 +1332,7 @@ handle_inferior_event (struct execution_ > /* If it's a new process, add it to the thread database */ > > ecs->new_thread_event = (!ptid_equal (ecs->ptid, inferior_ptid) > + && !ptid_equal (ecs->ptid, minus_one_ptid) > && !in_thread_list (ecs->ptid)); > > if (ecs->ws.kind != TARGET_WAITKIND_EXITED > Index: thread-db.c > =================================================================== > RCS file: /cvs/src/src/gdb/thread-db.c,v > retrieving revision 1.40 > diff -u -p -r1.40 thread-db.c > --- thread-db.c 25 May 2004 14:58:31 -0000 1.40 > +++ thread-db.c 4 Jun 2004 18:13:53 -0000 > @@ -252,7 +252,10 @@ thread_db_state_str (td_thr_state_e stat > > THP is a handle to the current thread; if INFOP is not NULL, the > struct thread_info associated with this thread is returned in > - *INFOP. */ > + *INFOP. > + > + If the thread is a zombie, TD_THR_ZOMBIE is returned. Otherwise, > + zero is returned to indicate success. */ > > static int > thread_get_info_callback (const td_thrhandle_t *thp, void *infop) > @@ -271,6 +274,16 @@ thread_get_info_callback (const td_thrha > thread_ptid = BUILD_THREAD (ti.ti_tid, GET_PID (inferior_ptid)); > thread_info = find_thread_pid (thread_ptid); > > + /* In the case of a zombie thread, don't continue. We don't want to > + attach to it thinking it is a new thread and we don't want to mark > + it as valid. */ > + if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE) > + { > + if (infop != NULL) > + *(struct thread_info **) infop = thread_info; > + return TD_THR_ZOMBIE; > + } > + > if (thread_info == NULL) > { > /* New thread. Attach to it now (why wait?). */ > @@ -355,7 +368,19 @@ thread_from_lwp (ptid_t ptid) > GET_LWP (ptid), thread_db_err_str (err)); > > thread_info = NULL; > - thread_get_info_callback (&th, &thread_info); > + > + /* Fetch the thread info. If we get back TD_THR_ZOMBIE, then the > + event thread has already died. If another gdb interface has called > + thread_alive() prior, the thread won't be found on the thread list > + anymore. In that case, we don't want to process this ptid anymore > + to avoid the possibility of later treating it as a newly > + discovered thread id that we should add to the list. Thus, > + we return a -1 ptid which is also how the thread list marks a > + dead thread. */ > + if (thread_get_info_callback (&th, &thread_info) == TD_THR_ZOMBIE > + && thread_info == NULL) > + return pid_to_ptid (-1); > + > gdb_assert (thread_info && thread_info->private->ti_valid); > > return BUILD_THREAD (thread_info->private->ti.ti_tid, GET_PID (ptid)); > @@ -950,7 +975,16 @@ thread_db_wait (ptid_t ptid, struct targ > if (!ptid_equal (trap_ptid, null_ptid)) > trap_ptid = thread_from_lwp (trap_ptid); > > - return thread_from_lwp (ptid); > + /* Change the ptid back into the higher level PID + TID format. > + If the thread is dead and no longer on the thread list, we will > + get back a dead ptid. This can occur if the thread death event > + gets postponed by other simultaneous events. In such a case, > + we want to just ignore the event and continue on. */ > + ptid = thread_from_lwp (ptid); > + if (GET_PID (ptid) == -1) > + ourstatus->kind = TARGET_WAITKIND_SPURIOUS; > + > + return ptid; > } > > static int