From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Triplett Subject: Re: "unexpected unlock" when unlocking, conditional, lock in loop Date: Sun, 7 Oct 2012 12:45:52 -0700 Message-ID: <20121007194552.GA909@leaf> References: <1349552876.20963@cat.he.net> <20121006202102.GA28179@leaf> <66AC2AD6-C0FA-4F60-850A-D8C9426184B8@coraid.com> <20121007023946.GA30713@leaf> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from relay4-d.mail.gandi.net ([217.70.183.196]:33935 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752627Ab2JGTp7 (ORCPT ); Sun, 7 Oct 2012 15:45:59 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-sparse-owner@vger.kernel.org List-Id: linux-sparse@vger.kernel.org To: Ed Cashin Cc: "linux-sparse@vger.kernel.org" On Sun, Oct 07, 2012 at 07:49:25AM -0500, Ed Cashin wrote: > On Oct 6, 2012, at 10:39 PM, Josh Triplett wrote: > > > On Sat, Oct 06, 2012 at 08:56:57PM -0500, Ed Cashin wrote: > ... > >> OK. From the sparse man page section on context, along with > >> include/linux/compiler.h, it sounds like the way to do exactly that > >> would be something unusual: > >> > >> int demofn(void) __attribute__((context(&lk,1,1))) > >> > >> ... but using that in demo.c causes sparse to warn me that it's > >> ignoring that attribute, so I doubt that can be what you mean. > > > > I did mean precisely that; I don't know why Sparse complains about that > > syntax. > > Maybe there's a header I need. Searching with cscope and ctags for definitions of "context" doesn't seem to be the right kind of searching. > > The complaint looks like: > > CC [M] drivers/block/aoe/demo.o > drivers/block/aoe/demo.c:9: warning: `context' attribute directive ignored > drivers/block/aoe/demo.c:9: error: expected `,' or `;' before `{' token > make[1]: *** [drivers/block/aoe/demo.o] Error 1 > make: *** [drivers/block/aoe/aoe.ko] Error 2 Oh, that complaint doesn't come from Sparse; that comes from GCC, since GCC doesn't understand the context attribute. Look at include/linux/compiler.h; it has wrapper macros for the various Sparse attributes, and defines them to nothing when not compiling with Sparse. If you want to use the context attribute to denote a lock held through a function, you need a patch like this: >From 0b862fc1a131a874d157420e9443f16a714596ef Mon Sep 17 00:00:00 2001 From: Josh Triplett Date: Sun, 7 Oct 2012 12:41:13 -0700 Subject: [PATCH] linux/compiler.h: Add __must_hold macro for functions called with a lock held linux/compiler.h has macros to denote functions that acquire or release locks, but not to denote functions called with a lock held that return with the lock still held. Add a __must_hold macro to cover this case. Signed-off-by: Josh Triplett --- include/linux/compiler.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index f430e41..b121554 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -10,6 +10,7 @@ # define __force __attribute__((force)) # define __nocast __attribute__((nocast)) # define __iomem __attribute__((noderef, address_space(2))) +# define __must_hold(x) __attribute__((context(x,1,1))) # define __acquires(x) __attribute__((context(x,0,1))) # define __releases(x) __attribute__((context(x,1,0))) # define __acquire(x) __context__(x,1) @@ -33,6 +34,7 @@ extern void __chk_io_ptr(const volatile void __iomem *); # define __chk_user_ptr(x) (void)0 # define __chk_io_ptr(x) (void)0 # define __builtin_warning(x, y...) (1) +# define __must_hold(x) # define __acquires(x) # define __releases(x) # define __acquire(x) (void)0