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Date: Wed, 4 Mar 2015 15:03:28 +0100 From: Daniel Wagner <daniel.wagner@...-carit.de> To: Jeff Layton <jlayton@...chiereds.net> CC: Andi Kleen <andi@...stfloor.org>, <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>, John Kacur <jkacur@...hat.com>, Alexander Viro <viro@...iv.linux.org.uk>, "J. Bruce Fields" <bfields@...ldses.org> Subject: Re: [RFC v1 0/5] fs/locks: Use plain percpu spinlocks instead of lglock to protect file_lock On 03/03/2015 01:29 AM, Jeff Layton wrote: >> Hmm, are you sure about that? I read the code this way that when a lock >> is added to flock_list it stays on that CPU. The locks are not moved >> from one flock_list to another during their existent. >> > > Yes, I'm sure. When a file lock is acquired, we assign the fl_link_cpu > to the current CPU and add it to the current CPU's global list. When > the lock is released, any blocked lock that might have been blocking on > it could acquire it at that point, and that doesn't necessarily occur > on the same CPU as where the lock was originally held. > > So, it's entirely possible that between when you drop the spinlock on > one CPU and pick it up on another, the lock could have been released > and then reacquired on a different CPU. D'oh. I am an idiot. I didn't really understand it the first time. Yes, you are right. cheers, daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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