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Message-ID: <20091019220129.GE4880@nowhere> Date: Tue, 20 Oct 2009 00:01:31 +0200 From: Frederic Weisbecker <fweisbec@...il.com> To: Thomas Gleixner <tglx@...utronix.de> Cc: John Kacur <jkacur@...hat.com>, linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>, Arnd Bergmann <arndbergmann@...glemail.com>, Ingo Molnar <mingo@...e.hu> Subject: Re: [PATCH RFC] PPC-BRIQ_PANEL: Remove BKL and replace with atomic variable. On Mon, Oct 19, 2009 at 07:04:02AM +0200, Thomas Gleixner wrote: > B1;2005;0cOn Sun, 18 Oct 2009, John Kacur wrote: > > > >From b64c7d0f11eab96cb253b23c7264c999746116c0 Mon Sep 17 00:00:00 2001 > > From: John Kacur <jkacur@...hat.com> > > Date: Sun, 18 Oct 2009 21:29:21 +0200 > > Subject: [PATCH] PPC-BRIQ_PANEL: Remove BKL and replace with atomic variable. > > > > There are no locks here except the bkl in briq_panel_open. It's only > > purpose is to ensure single access. Remove the bkl and ensure single access > > by making vfd_is_open an atomic_variable. > > And again, can you please look more carefully at the init > vs. read/write functions ? > > The BKL is not only protecting the single user variable it's also > serializing write against the access to the display in init. > > Thanks, > > tglx That could be solved by statically initializing vfd_is_open to -1 and then set it to 0 once briq_panel_init has finished initializing the device. Another thing, I really don't see the point in this check in briq_panel_read() and briq_panel_write(): if (!vfd_is_open) return -ENODEV; You can't read/write if vfd_is_open hasn't been set to 1 (open set) and you're not racing against the release callback since it is called after the file is closed. I guess this check can disappear from read/write callbacks. -- 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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