linux-kernel - Re: sparse breakage triggered by rcu_read

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Date:	Thu, 18 Oct 2007 10:41:15 -0700
From:	Josh Triplett <josh@...edesktop.org>
To:	Alexey Dobriyan <adobriyan@...ru>
CC:	linux-sparse@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: sparse breakage triggered by rcu_read_lock() lockdep annotations

Alexey Dobriyan 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

Thanks for the detailed report.  Looking into it now.

- Josh Triplett



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