From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:54967) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ra0pi-0002N3-4g for qemu-devel@nongnu.org; Mon, 12 Dec 2011 03:01:59 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ra0pd-0007v2-VG for qemu-devel@nongnu.org; Mon, 12 Dec 2011 03:01:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3850) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ra0pd-0007uo-Oc for qemu-devel@nongnu.org; Mon, 12 Dec 2011 03:01:53 -0500 Message-ID: <4EE5B4EB.70609@redhat.com> Date: Mon, 12 Dec 2011 09:01:47 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1323315400-25585-1-git-send-email-mdroth@linux.vnet.ibm.com> <1323316087-1070-1-git-send-email-mdroth@linux.vnet.ibm.com> In-Reply-To: <1323316087-1070-1-git-send-email-mdroth@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3] network scripts: don't block SIGCHLD before forking List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Roth Cc: jan.kiszka@siemens.com, qemu-devel@nongnu.org On 12/08/2011 04:48 AM, Michael Roth wrote: > This patch fixes a bug where child processes of launch_script() can > misbehave due to SIGCHLD being blocked. In the case of `sudo`, this > causes a permanent hang. > > Previously a SIGCHLD handler was added to reap fork_exec()'d zombie > processes by calling waitpid(-1, ...). This required other > fork()/waitpid() callers to temporarilly block SIGCHILD to avoid > having the final wait status being intercepted by the SIGCHLD > handler: > > 7c3370d4fe3fa6cda8655f109e4659afc8ca4269 > > Since then, the qemu_add_child_watch() interface was added to allow > registration of such processes and reap only from that specific set > of PIDs: > > 4d54ec7898bd951007cb6122d5315584bd41d0c4 > > As a result, we can now avoid blocking SIGCHLD in launch_script(), so > drop that behavior. > > Signed-off-by: Michael Roth > --- > net/tap.c | 6 ------ > 1 files changed, 0 insertions(+), 6 deletions(-) > > diff --git a/net/tap.c b/net/tap.c > index 1f26dc9..6c27a94 100644 > --- a/net/tap.c > +++ b/net/tap.c > @@ -346,15 +346,10 @@ static TAPState *net_tap_fd_init(VLANState *vlan, > > static int launch_script(const char *setup_script, const char *ifname, int fd) > { > - sigset_t oldmask, mask; > int pid, status; > char *args[3]; > char **parg; > > - sigemptyset(&mask); > - sigaddset(&mask, SIGCHLD); > - sigprocmask(SIG_BLOCK,&mask,&oldmask); > - > /* try to launch network script */ > pid = fork(); > if (pid == 0) { > @@ -378,7 +373,6 @@ static int launch_script(const char *setup_script, const char *ifname, int fd) > while (waitpid(pid,&status, 0) != pid) { > /* loop */ > } > - sigprocmask(SIG_SETMASK,&oldmask, NULL); > > if (WIFEXITED(status)&& WEXITSTATUS(status) == 0) { > return 0; Reviewed-by: Paolo Bonzini Paolo