"ps -e" without procfs(5)

[Mikolaj Golub]

On Wed, 09 Nov 2011 15:31:26 +0200 Mikolaj Golub wrote:

 MG> On Wed, 9 Nov 2011 14:53:29 +0200 Kostik Belousov wrote:

 >>> And now you return success and nothing gets copied out for the process
 >>> in P_INEXEC state. Either you should return an error like EAGAIN, or
 >>> consider the P_INEXEC state as transitional and wait till process
 >>> leaves it. Or, ignore the state as it was before, and return whatever
 >>> error proc_rwmem generated (my preference).

 KB>> Forgot to say that the check does not change much because you drop
 KB>> process lock immediately after the check, so the process may enter
 KB>> the INEXEC state right after the check. I believe you already tried
 KB>> to do this with P_WEXIT.

 MG> Good point :-). Although after adding the P_INEXEC I have not seen errors any
 MG> more, while before they were often (when running 'procstat -ca' in loop and
 MG> building world simultaneously). Thus it looks like the probability is much
 MG> smaller.

 MG> So, it still looks good for me to check for P_INEXEC and return EAGAIN, and
 MG> add the comment why we do this and that it still racy. But if you still think
 MG> that ignoring the state is the best option no problems for me to return it
 MG> back.

Realted to this, sysctl_kern_proc_kstack() looks like has the similar issue.
But it returns ESRCH instead.

	/* XXXRW: Not clear ESRCH is the right error during proc execve(). */
	if (p->p_flag & P_WEXIT || p->p_flag & P_INEXEC) {
		PROC_UNLOCK(p);
		return (ESRCH);
	}
        ...
	_PHOLD(p);
	PROC_UNLOCK(p);

-- 
Mikolaj Golub