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Move cpu_exit() earlier in exit1() to close a race between

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SIGCHLD/kevent(2) notification of process termination and wait().  Now
we no longer drop locks between sending the notification and marking
the process as a zombie.  Previously, if another process attempted to do
a wait() with W_NOHANG after receiving a SIGCHLD or kevent and locked
the process while the exiting thread was in cpu_exit(), then wait() would
fail to find the process, which is quite astonishing to the process
calling wait().

MFC after:	3 days
This commit is contained in:
jhb 2007-05-14 22:21:58 +00:00
parent 2b1170b7f0
commit 77d161b46b
1 changed files with 10 additions and 16 deletions
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26
sys/kern/kern_exit.c
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@ -405,6 +405,16 @@ exit1(struct thread *td, int rv)
LIST_REMOVE(p, p_hash);
sx_xunlock(&allproc_lock);
/*
* Call machine-dependent code to release any
* machine-dependent resources other than the address space.
* The address space is released by "vmspace_exitfree(p)" in
* vm_waitproc().
*/
cpu_exit(td);
WITNESS_WARN(WARN_PANIC, NULL, "process (pid %d) exiting", p->p_pid);
/*
* Reparent all of our children to init.
*/
@ -484,22 +494,6 @@ exit1(struct thread *td, int rv)
else /* LINUX thread */
psignal(p->p_pptr, p->p_sigparent);
}
PROC_UNLOCK(p->p_pptr);
PROC_UNLOCK(p);
/*
* Finally, call machine-dependent code to release the remaining
* resources including address space.
* The address space is released by "vmspace_exitfree(p)" in
* vm_waitproc().
*/
cpu_exit(td);
WITNESS_WARN(WARN_PANIC, &proctree_lock.lock_object,
"process (pid %d) exiting", p->p_pid);
PROC_LOCK(p);
PROC_LOCK(p->p_pptr);
sx_xunlock(&proctree_lock);
/*