sparse breakage triggered by rcu_read_lock() lockdep annotations

From: Alexey Dobriyan
Date: Tue Oct 16 2007 - 06:55:40 EST


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

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