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Biederman" Cc: geert@linux-m68k.org, vverma@digitalocean.com, hdanton@sina.com, hch@infradead.org, stefanha@redhat.com, jasowang@redhat.com, mst@redhat.com, sgarzare@redhat.com, virtualization@lists.linux-foundation.org, christian.brauner@ubuntu.com, axboe@kernel.dk, linux-kernel@vger.kernel.org References: <20211129194707.5863-1-michael.christie@oracle.com> <87tuf79gni.fsf@email.froward.int.ebiederm.org> <87tuf11oe6.fsf@email.froward.int.ebiederm.org> <87pmpoxzuf.fsf@email.froward.int.ebiederm.org> <783145b7-243b-b85e-e274-44ef6c0696b9@oracle.com> <874k62b76d.fsf@email.froward.int.ebiederm.org> From: Mike Christie In-Reply-To: <874k62b76d.fsf@email.froward.int.ebiederm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: CH2PR08CA0026.namprd08.prod.outlook.com (2603:10b6:610:5a::36) To DM5PR10MB1466.namprd10.prod.outlook.com (2603:10b6:3:b::7) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 6c462a9f-d317-446a-b2d6-08d9dab38971 X-MS-TrafficTypeDiagnostic: DS7PR10MB5360:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8273; 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Biederman wrote: > Mike Christie writes: > >> On 12/22/21 12:24 PM, Eric W. Biederman wrote: >>> All I am certain of is that you need to set >>> "args->exit_signal = -1;". This prevents having to play games with >>> do_notify_parent. >> >> Hi Eric, >> >> I have all your review comments handled except this one. It's looking like it's >> more difficult than just setting the exit_signal=-1, so I wanted to check that >> I understood you. > > [snip problems with exit_signal = -1] > >> >> What do you think? > > I was wrong. I appear to have confused the thread and the non-thread > cases. > > Perhaps I meant "args->exit_signal = 0". That looks like > do_notify_parent won't send it, and thread_group_leader continues to do > the right thing. That doesn't work too. exit_notify will call do_notify_parent but our parent, qemu, does not ignore SIGCHILD so we will not drop down in into this chunk: psig = tsk->parent->sighand; spin_lock_irqsave(&psig->siglock, flags); if (!tsk->ptrace && sig == SIGCHLD && (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) { do_notify_parent will return false and so autoreap in exit_notify will be false. > > Baring any additional confusion on my part that cleanly solves the > problem of how not to send a signal from a child process cleanly. > > My apologies for sending you on a wild goose chase. > It's no problem. I learned a lot about signal handling :)