From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 87692 invoked by alias); 3 Mar 2015 11:55:33 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 87683 invoked by uid 89); 3 Mar 2015 11:55:32 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 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 (AES256-GCM-SHA384 encrypted) ESMTPS; Tue, 03 Mar 2015 11:55:31 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t23BtTEa008011 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 3 Mar 2015 06:55:29 -0500 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t23BtRwo026164; Tue, 3 Mar 2015 06:55:28 -0500 Message-ID: <54F5A12F.9000702@redhat.com> Date: Tue, 03 Mar 2015 11:55:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: "Metzger, Markus T" CC: "gdb-patches@sourceware.org" Subject: Re: [PATCH] btrace: avoid tp != NULL assertion References: <1423473902-2286-1-git-send-email-markus.t.metzger@intel.com> <54F4DF9D.3060400@redhat.com> In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2015-03/txt/msg00064.txt.bz2 On 03/03/2015 10:49 AM, Metzger, Markus T wrote: > I have no idea how regcache->ptid ended up with lwp=0. > > Here's the full backtrace in case it helps. Yes it does. > #6 0x0827a106 in i386_linux_resume (ops=0x9737ca0 , ptid=..., step=1, > signal=GDB_SIGNAL_0) at gdb/i386-linux-nat.c:670 > #7 0x08280c12 in linux_resume_one_lwp (lp=0x9a0a5b8, step=1, signo=GDB_SIGNAL_0) > at gdb/linux-nat.c:1529 Frame #7 where we convert the ptid to something inf-ptrace.c understands. The fix is just to stop losing information. This also improves performance a tiny bit, as currently we fetch registers out of ptrace twice, once for {pid,lwp} in linux-nat.c, and another for {pid,0} in inf-ptrace/i386-linux-nat.c. We'll now use a single regcache object everywhere. Please try the patch below. Note that this in your patch: + lwp = ptid_get_lwp (ptid); + if (lwp == 0) + { + int pid; + + /* Not a threaded program. Use the PID as LWP ID. */ + pid = ptid_get_pid (ptid); + ptid = ptid_build (pid, pid, 0); + } + + return find_thread_ptid (ptid); +} + is wrong because when debugging a multi-threaded program, you'll have e.g. ({pid,lwp}) {1,1}, {1,2}, {1,3}, etc. Your patch makes btrace look for {2,2}, {3,3}, etc. in the thread list, which just aren't there, and thus return NULL. I assume that that's why you needed to downgrade the asserts to errors. ---- >From 6f4e842f2cfefa18d789d2b658e2719fa5609e60 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Tue, 3 Mar 2015 11:03:34 +0000 Subject: [PATCH] No longer hack ptids when passing the request down to the inf-ptrace layer --- gdb/i386-linux-nat.c | 5 ++--- gdb/inf-ptrace.c | 25 ++++++++++++++++++++++--- gdb/linux-nat.c | 6 +----- 3 files changed, 25 insertions(+), 11 deletions(-) diff --git a/gdb/i386-linux-nat.c b/gdb/i386-linux-nat.c index b95b47e..8cb8c66 100644 --- a/gdb/i386-linux-nat.c +++ b/gdb/i386-linux-nat.c @@ -648,8 +648,7 @@ static void i386_linux_resume (struct target_ops *ops, ptid_t ptid, int step, enum gdb_signal signal) { - int pid = ptid_get_pid (ptid); - + int pid = ptid_get_lwp (ptid); int request; if (catch_syscall_enabled () > 0) @@ -659,7 +658,7 @@ i386_linux_resume (struct target_ops *ops, if (step) { - struct regcache *regcache = get_thread_regcache (pid_to_ptid (pid)); + struct regcache *regcache = get_thread_regcache (ptid); struct gdbarch *gdbarch = get_regcache_arch (regcache); enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); ULONGEST pc; diff --git a/gdb/inf-ptrace.c b/gdb/inf-ptrace.c index 4c22a84..606bdb4 100644 --- a/gdb/inf-ptrace.c +++ b/gdb/inf-ptrace.c @@ -289,6 +289,22 @@ inf_ptrace_stop (struct target_ops *self, ptid_t ptid) kill (-inferior_process_group (), SIGINT); } +/* Return which PID to pass to ptrace in order to observe/control the + tracee identified by PTID. */ + +static pid_t +get_ptrace_pid (ptid_t ptid) +{ + pid_t pid; + + /* If we have an LWPID to work with, use it. Otherwise, we're + dealing with a non-threaded program/target. */ + pid = ptid_get_lwp (ptid); + if (pid == 0) + pid = ptid_get_pid (ptid); + return pid; +} + /* Resume execution of thread PTID, or all threads if PTID is -1. If STEP is nonzero, single-step it. If SIGNAL is nonzero, give it that signal. */ @@ -297,13 +313,16 @@ static void inf_ptrace_resume (struct target_ops *ops, ptid_t ptid, int step, enum gdb_signal signal) { - pid_t pid = ptid_get_pid (ptid); + pid_t pid; + int request; - if (pid == -1) + if (ptid_equal (minus_one_ptid, ptid)) /* Resume all threads. Traditionally ptrace() only supports single-threaded processes, so simply resume the inferior. */ - pid = ptid_get_pid (inferior_ptid); + pid = get_ptrace_pid (inferior_ptid); + else + pid = get_ptrace_pid (ptid); if (catch_syscall_enabled () > 0) request = PT_SYSCALL; diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c index 2e1133d..cb10e2c 100644 --- a/gdb/linux-nat.c +++ b/gdb/linux-nat.c @@ -1506,8 +1506,6 @@ linux_nat_detach (struct target_ops *ops, const char *args, int from_tty) static void linux_resume_one_lwp (struct lwp_info *lp, int step, enum gdb_signal signo) { - ptid_t ptid; - lp->step = step; /* stop_pc doubles as the PC the LWP had when it was last resumed. @@ -1524,9 +1522,7 @@ linux_resume_one_lwp (struct lwp_info *lp, int step, enum gdb_signal signo) if (linux_nat_prepare_to_resume != NULL) linux_nat_prepare_to_resume (lp); - /* Convert to something the lower layer understands. */ - ptid = pid_to_ptid (ptid_get_lwp (lp->ptid)); - linux_ops->to_resume (linux_ops, ptid, step, signo); + linux_ops->to_resume (linux_ops, lp->ptid, step, signo); lp->stop_reason = LWP_STOPPED_BY_NO_REASON; lp->stopped = 0; registers_changed_ptid (lp->ptid); -- 1.9.3