Messages in this thread Patch in this message | | | Date | Mon, 24 Feb 2014 20:27:34 +0100 | From | Guillaume Morin <> | Subject | [PATCH] exit.c: call proc_exit_connector() after exit_state is set |
| |
From: Guillaume Morin <guillaume@morinfr.org>
The process events connector delivers a notification when a process exits. This is really convenient for a process that spawns and wants to monitor its children through an epoll-able() interface.
Unfortunately, there is a small window between when the event is delivered and the child become wait()-able.
This is creates a race if the parent wants to make sure that it knows about the exit, e.g
pid_t pid = fork(); if (pid > 0) { register_interest_for_pid(pid); if (waitpid(pid, NULL, WNOHANG) > 0) { /* We might have raced with exit() */ } return; }
/* Child */ execve(...)
register_interest_for_pid() would be telling the the connector socket reader to pay attention to events related to pid.
Though this is not a bug, I think it would make the connector a bit more usable if this race was closed by simply moving the call to proc_exit_connector() from just before exit_notify() to right after.
Signed-off-by: Guillaume Morin <guillaume@morinfr.org> Cc: matt.helsley@gmail.com --- diff --git a/kernel/exit.c b/kernel/exit.c index 1e77fc6..9b0ac8c 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -804,7 +804,6 @@ void do_exit(long code) module_put(task_thread_info(tsk)->exec_domain->module); - proc_exit_connector(tsk); /* * FIXME: do that only when needed, using sched_exit tracepoint @@ -812,6 +811,7 @@ void do_exit(long code) flush_ptrace_hw_breakpoint(tsk); exit_notify(tsk, group_dead); + proc_exit_connector(tsk); #ifdef CONFIG_NUMA task_lock(tsk); mpol_put(tsk->mempolicy);
-- Guillaume Morin <guillaume@morinfr.org>
| |