From: Pavel Emelianov <xemul@sw.ru>
To: "Eric W. Biederman" <ebiederm@xmission.com>,
Sukadev Bhattiprolu <sukadev@us.ibm.com>,
Serge Hallyn <serue@us.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [RFC] kernel/pid.c pid allocation wierdness
Date: Wed, 14 Mar 2007 10:30:59 +0300 [thread overview]
Message-ID: <45F7A4B3.5040005@sw.ru> (raw)
Hi.
I'm looking at how alloc_pid() works and can't understand
one (simple/stupid) thing.
It first kmem_cache_alloc()-s a strct pid, then calls
alloc_pidmap() and at the end it taks a global pidmap_lock()
to add new pid to hash.
The question is - why does alloc_pidmap() use at least
two atomic ops and potentially loop to find a zero bit
in pidmap? Why not call alloc_pidmap() under pidmap_lock
and find zero pid in pidmap w/o any loops and atomics?
The same is for free_pid(). Do I miss something?
Thank,
Pavel
next reply other threads:[~2007-03-14 7:29 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-14 7:30 Pavel Emelianov [this message]
2007-03-14 14:12 ` [RFC] kernel/pid.c pid allocation wierdness Eric W. Biederman
2007-03-14 15:03 ` William Lee Irwin III
2007-03-14 16:54 ` Eric W. Biederman
2007-03-15 20:26 ` William Lee Irwin III
2007-03-16 13:04 ` Eric W. Biederman
2007-03-16 19:46 ` William Lee Irwin III
2007-03-16 21:18 ` Eric W. Biederman
2007-03-14 15:33 ` Oleg Nesterov
2007-03-16 10:57 ` Pavel Emelianov
2007-03-16 11:37 ` Eric Dumazet
2007-03-16 11:58 ` Pavel Emelianov
2007-03-16 11:40 ` Dmitry Adamushko
2007-03-14 14:43 ` William Lee Irwin III
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