From: Guillaume Morin <guilla...@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 <guilla...@morinfr.org>
Cc: matt.hels...@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 <guilla...@morinfr.org>
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