From: "David S. Miller" <davem@redhat.com>
To: kanoj@google.engr.sgi.com
Cc: jakub@redhat.com, linux-kernel@vger.rutgers.edu, linux-mm@kvack.org
Subject: Re: 2.3 Pagedir allocation/free and update races
Date: Tue, 14 Dec 1999 15:08:02 -0800 [thread overview]
Message-ID: <199912142308.PAA01037@pizda.ninka.net> (raw)
In-Reply-To: <199912142300.PAA05447@google.engr.sgi.com> (kanoj@google.engr.sgi.com)
Yes, I am sorry for the misleading logic in my note. Per-cpu caches are
safe (I wonder why it was taken out for i386). For architectures that
have to do set_pgdir() though, the pgdir update code might be racy,
unless the arch code has locks to protect the page directory scanning.
Btw, Linus indicated to me he ran into problems with the patch, and
will be pulling it out in the next pre-release. I will take a closer look
at the code.
Just handle the set_pgdir() stuff like this:
pgcache_update_flag = 0;
smp_call_func(ALL_CPUS, update_pgcaches_and_wait_on_flag);
update_local_pgcache();
pgcache_update_flag = 1;
for_each_task(tsk)
update_pgdir(tsk);
That should give the correct synchronization with zero cost
for the fast normal paths which can rely solely on the cpu
localness of the data structure.
Later,
David S. Miller
davem@redhat.com
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next prev parent reply other threads:[~1999-12-14 23:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-12-14 9:46 Kanoj Sarcar
1999-12-14 9:55 ` David S. Miller
1999-12-14 10:13 ` Jakub Jelinek
1999-12-14 23:00 ` Kanoj Sarcar
1999-12-14 23:08 ` David S. Miller [this message]
1999-12-14 23:51 ` Kanoj Sarcar
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