From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16717 invoked by alias); 20 Nov 2008 13:28:47 -0000 Received: (qmail 16675 invoked by uid 22791); 20 Nov 2008 13:28:46 -0000 X-Spam-Check-By: sourceware.org Received: from mail.codesourcery.com (HELO mail.codesourcery.com) (65.74.133.4) by sourceware.org (qpsmtpd/0.31) with ESMTP; Thu, 20 Nov 2008 13:28:06 +0000 Received: (qmail 17070 invoked from network); 20 Nov 2008 13:28:04 -0000 Received: from unknown (HELO orlando.local) (pedro@127.0.0.2) by mail.codesourcery.com with ESMTPA; 20 Nov 2008 13:28:04 -0000 From: Pedro Alves To: gdb-patches@sourceware.org Subject: Fix foll-fork.exp foll-vfork.exp fork-child-threads.exp Date: Thu, 20 Nov 2008 19:15:00 -0000 User-Agent: KMail/1.9.10 MIME-Version: 1.0 Content-Type: Multipart/Mixed; boundary="Boundary-00=_tXWJJsQSBfzVBV9" Message-Id: <200811201328.13651.pedro@codesourcery.com> X-IsSubscribed: yes 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 X-SW-Source: 2008-11/txt/msg00553.txt.bz2 --Boundary-00=_tXWJJsQSBfzVBV9 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Content-length: 943 Long story short: After following a child, detaching from the parent, ('set follow-fork-mode child' + 'set detach-on-fork on') here in this bit, infrun.c:resume(): { .... follow_fork (); ... tp->stop_signal = TARGET_SIGNAL_0; } ... `tp' is no longer in the thread list (it was pointing at a thread of the parent process, which we've detached from, hence no longer in the thread list), so if the assignment above doesn't crash, it ends up writing to who-knows-where. With some local changes I was making, sometimes, `tp' happened to be left pointing at linux_nat.c:lwp_list, and so that assignment above ended up clearing lp->waitstatus.kind (of the first lwp in the list), which resulted in GDB considering that the child process had exited (because TARGET_SIGNAL_0 == TARGET_WAITKIND_EXITED). This should fix intermittent foll-fork.exp foll-vfork.exp fork-child-threads.exp failures. Checked in. -- Pedro Alves --Boundary-00=_tXWJJsQSBfzVBV9 Content-Type: text/x-diff; charset="iso 8859-15"; name="foll_fork_dang.diff" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="foll_fork_dang.diff" Content-length: 1216 2008-11-20 Pedro Alves * infrun.c (resume): If following a fork, reread the current thread. Avoid dereferencing a possibly dangling pointer. --- gdb/infrun.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) Index: src/gdb/infrun.c =================================================================== --- src.orig/gdb/infrun.c 2008-11-20 05:37:35.000000000 +0000 +++ src/gdb/infrun.c 2008-11-20 12:30:26.000000000 +0000 @@ -1053,6 +1053,9 @@ a command like `return' or `jump' to con pending_follow.kind = TARGET_WAITKIND_SPURIOUS; if (follow_fork ()) should_resume = 0; + + /* Following a fork may change inferior_ptid. */ + tp = inferior_thread (); break; case TARGET_WAITKIND_EXECD: @@ -1148,11 +1151,11 @@ a command like `return' or `jump' to con displaced_step_dump_bytes (gdb_stdlog, buf, sizeof (buf)); } - target_resume (resume_ptid, step, sig); - /* Avoid confusing the next resume, if the next stop/resume happens to apply to another thread. */ tp->stop_signal = TARGET_SIGNAL_0; + + target_resume (resume_ptid, step, sig); } discard_cleanups (old_cleanups); --Boundary-00=_tXWJJsQSBfzVBV9--