linux-kernel - [PATCH] Re: sparse breakage triggered by rcu_read

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Date:	Fri, 19 Oct 2007 14:08:16 -0700
From:	"Christopher Li" <sparse@...isli.org>
To:	"Alexey Dobriyan" <adobriyan@...ru>,
	"Josh Triplett" <josh@...edesktop.org>
Cc:	linux-sparse@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Re: sparse breakage triggered by rcu_read_lock() lockdep annotations

OK, I get a trivial fix after all. The test case is fixed now.
I haven't done much test otherwise.

See the patch attached.

Chris


On 10/19/07, Chris Li <christ.li@...il.com> wrote:
> Err,
>
> Sparse does not support the local label syntax yet. It just treats the
> second label "x:" as the same as the first one. Then the linearize
> code gets serious confused when it saw one label get define in two
> places.
>
> The fix seems not trivial from the first look.
>
> Chris
>
> On 10/16/07, Alexey Dobriyan <adobriyan@...ru> wrote:
> > FWIW, commit 851a67b825540a8e00c0be3ee25e4627ba8b133b
> > aka "lockdep: annotate rcu_read_{,un}lock{,_bh}"
> > causes sparse to trigger internal assertion in quite a few places over
> > allyesconfig run.
> >
> >         sparse: flow.c:805: rewrite_parent_branch: Assertion `changed' failed.
> >
> > Trimmed down testcase:
> >
> >         void f(unsigned long ip);
> >         static void g(void)
> >         {
> >                 if (1) {
> >                       f(({ __label__ x; x: (unsigned long)&&x; }));
> >                 }
> >                 f(({ __label__ x; x: (unsigned long)&&x; }));
> >         }
> >
> > #0  0x4001c410 in __kernel_vsyscall ()
> > (gdb) bt
> > #0  0x4001c410 in __kernel_vsyscall ()
> > #1  0x40050701 in raise () from /lib/libc.so.6
> > #2  0x40051e38 in abort () from /lib/libc.so.6
> > #3  0x40049fcc in __assert_fail () from /lib/libc.so.6
> > #4  0x08064947 in pack_basic_blocks (ep=0x411a1c6c) at flow.c:812
> > #5  0x0805ffbf in linearize_symbol (sym=0x4103ec8c) at linearize.c:2154
> > #6  0x080492a3 in main (argc=Cannot access memory at address 0x274d) at sparse.c:266
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-sparse" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
>

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