From patchwork Wed Aug 8 12:30:59 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Burgess X-Patchwork-Id: 28787 Received: (qmail 126155 invoked by alias); 8 Aug 2018 12:31:07 -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 126139 invoked by uid 89); 8 Aug 2018 12:31:06 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.2 spammy=preference, removable, connecting, cleaned X-HELO: mail-wr1-f68.google.com Received: from mail-wr1-f68.google.com (HELO mail-wr1-f68.google.com) (209.85.221.68) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 08 Aug 2018 12:31:04 +0000 Received: by mail-wr1-f68.google.com with SMTP id v14-v6so1870104wro.5 for ; Wed, 08 Aug 2018 05:31:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=embecosm.com; s=google; h=date:from:to:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=vDX7idEoUrNaJbX91hvTElkgTiA+OgBLGpiZ1qJaXTw=; b=C6EY649n++8Dq0utNio/JBuVtCK80AWnE+MkmRDi0zPktOU52zgvy1CYGpptvrvtYh KTkvFvc8Y4X/LATdEWnUbjHQSJXnmTxsWNU6/3vK5IwD8SANCdkOuboaefCE9+TkmIQc luMFKv7SNDL5+gCURyS7yZt0GwPrM5t6hJxSxQKpJuPOEIP3YTQnt7XQaSYFWYFMZlLM QoVG4cMfXQ86Jh1JT6tP9FrqmoiMiJbghonwBEPv25G16+kd+yvfuZo5gD8LVnCJ1qAt b7LRj/KrP2GXs0nGWuG/Wb5jOuOKhNU7PInPOmK1nw9E9xB8Ez8cNBu7KspGPUH4MZXc yUuA== Return-Path: Received: from localhost (host81-140-215-41.range81-140.btcentralplus.com. [81.140.215.41]) by smtp.gmail.com with ESMTPSA id e141-v6sm7474421wmd.32.2018.08.08.05.31.00 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 08 Aug 2018 05:31:00 -0700 (PDT) Date: Wed, 8 Aug 2018 13:30:59 +0100 From: Andrew Burgess To: gdb-patches@sourceware.org Subject: Re: [PATCHv2 2/2] gdb: Clean up inferior list when reconnecting to new target Message-ID: <20180808123059.GJ3155@embecosm.com> References: <20180717174744.GJ2888@embecosm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Fortune: Some Windows were made to be broken. X-Editor: GNU Emacs [ http://www.gnu.org/software/emacs ] User-Agent: Mutt/1.9.2 (2017-12-15) X-IsSubscribed: yes After pushing the first patch with a change of location for the test, this patch needed updating. Nothing else has changed except the location of the modified test script. Thanks, Andrew --- gdb: Clean up inferior list when reconnecting to new target When connected to a target and running an inferior, if the inferior forks then a new, inferior is created to track the child process. Usually the second inferior (the child process) will be automatically cleaned up (removed) by GDB once the child has completed. However, if we connect to a new target then the second inferior is left around, and we can even end up using the second inferior in order to run a program on the new target, for example in this session: (gdb) target extended-remote :2347 (gdb) file /path/to/exe (gdb) set remote exec-file /path/to/exe (gdb) set detach-on-fork off (gdb) break breakpt (gdb) run # ... hits breakpoint (gdb) info inferiors Num Description Executable * 1 process 15406 /path/to/exe 2 process 15407 /path/to/exe (gdb) kill Kill the program being debugged? (y or n) y (gdb) info inferiors Num Description Executable * 1 /path/to/exe 2 process 15433 /path/to/exe (gdb) target extended-remote :2348 (gdb) file /path/to/exe (gdb) set remote exec-file /path/to/exe (gdb) run # ... hits breakpoint (gdb) info inferiors Num Description Executable 1 /path/to/exe * 2 process 15408 /path/to/exe 3 process 15409 /path/to/exe (gdb) Notice how after connecting to the second extended-remote target, and then running the test program we now have inferiors 1, 2, and 3. There's nothing really _wrong_ with this, but a better experience would, I think, be to have only inferiors 1 and 2 in the new target's session. The issue here is that in target.c:dispose_inferior GDB uses switch_to_thread, which also switches the current inferior. This leaves the last inferior in the list selected after target.c:target_preopen has completed. We could change target.c:dispose_inferior to ensure the selected inferior is not left changed, however, in the above example, I think that, even if the user manually selected inferior 2 _before_ connecting to the new target, the best behaviour would still be for GDB to switch back to inferior 1. This seems to suggest that the right thing to do is have GDB _choose_ a new inferior as part of target_preopen, after which is can call prune_inferiors to remove transient inferiors from the list. An existing test is extended to cover this behaviour. gdb/ChangeLog: * target.c (find_first_killed_inferior): New function. (target_preopen): Use find_first_killed_inferior to reset selected inferior, and prune killed inferior as appropriate. gdb/testsuite/ChangeLog: * gdb.server/extended-remote-restart.exp: Extend. --- gdb/ChangeLog | 6 ++++ gdb/target.c | 35 ++++++++++++++++++++++ gdb/testsuite/ChangeLog | 4 +++ .../gdb.server/extended-remote-restart.exp | 6 ++++ 4 files changed, 51 insertions(+) diff --git a/gdb/target.c b/gdb/target.c index 115e9ae4948..7dfb5693f11 100644 --- a/gdb/target.c +++ b/gdb/target.c @@ -2043,6 +2043,31 @@ dispose_inferior (struct inferior *inf, void *args) return 0; } +/* Callback for iterate_over_inferiors. Record in ARG the first killed + inferior. If we find an inferior that is both killed and not removable, + this is returned in preference. The definition of "first" here is + pretty loose, and depends on the order in the inferior list. */ + +static int +find_first_killed_inferior (struct inferior *inf, void *arg) +{ + struct inferior **infp = (struct inferior **) arg; + + if (inf->pid == 0) + { + if (!inf->removable) + { + *infp = inf; + return 1; + } + else if (*infp == nullptr) + *infp = inf; + } + + return 0; +} + + /* This is to be called by the open routine before it does anything. */ @@ -2059,6 +2084,16 @@ target_preopen (int from_tty) iterate_over_inferiors (dispose_inferior, NULL); else error (_("Program not killed.")); + + /* The call to DISPOSE_INFERIOR will leave the last inferior we + killed selected. Reset the selection to the earliest inferior + that is killed and not removable. The prune any other killed + inferiors. */ + struct inferior *inf = nullptr; + iterate_over_inferiors (find_first_killed_inferior, &inf); + if (inf != nullptr) + set_current_inferior (inf); + prune_inferiors (); } /* Calling target_kill may remove the target from the stack. But if diff --git a/gdb/testsuite/gdb.server/extended-remote-restart.exp b/gdb/testsuite/gdb.server/extended-remote-restart.exp index 39fcb9e2e58..fb4bdd1755c 100644 --- a/gdb/testsuite/gdb.server/extended-remote-restart.exp +++ b/gdb/testsuite/gdb.server/extended-remote-restart.exp @@ -119,6 +119,12 @@ proc test_reload { do_kill_p follow_child_p } { } else { fail "reconnect after fork" } + + gdb_test "info inferiors" \ + [multi_line \ + " Num Description Executable.*" \ + "\\* 1 +${dead_inf_ptn} \[^\r\n\]+" ] \ + "Check inferiors after reconnect" } # Run all combinations of the test.