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From: Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de>
Date: Sat, 28 Oct 2000 17:42:50 +0200
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To: Mark Hahn <hahn@coffee.psychology.mcmaster.ca>
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In-Reply-To: <Pine.LNX.4.10.10010281042130.8717-100000@coffee.psychology.mcmaster.ca>
Subject: Re: question on SMP and read()/write()
Cc: linux-kernel@vger.kernel.org
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On Saturday 28 October 2000 16:43, you wrote:
> > I've noticed that sys_read() and sys_write() don't grab the big kernel
> > lock. As file descriptors may be shared, must device drivers provide SMP
> > safe read() and write() methods ?
>
> no.  FD's refer to files; block drivers don't, and the nontrivial
> code between sys_* and drivers deals with this sort of thing.

Sure block drivers need not do this, but how about drivers for character 
devices ? It seems that sys_read() calls a function provided by the
f_op table without any locking. Isn't this the function a driver for a 
character device must provide to the VFS ?

	TIA
		Oliver
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