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| author | Alexander Chumachenko <ledest@gmail.com> | 2010-04-01 15:34:52 +0300 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2010-09-26 22:43:07 -0700 |
| commit | c9e2fbd909c20b165b2b9ffb59f8b674cf0a55b0 (patch) | |
| tree | 29b4f977e3a1fa4b0b85057c35652ee5fe58949e /CREDITS | |
| parent | 7329cf0201f48695862e334828a108aa7175e955 (diff) | |
| download | linux-c9e2fbd909c20b165b2b9ffb59f8b674cf0a55b0.tar.bz2 | |
x86: Avoid 'constant_test_bit()' misoptimization due to cast to non-volatile
While debugging bit_spin_lock() hang, it was tracked down to gcc-4.4
misoptimization of non-inlined constant_test_bit() due to non-volatile
addr when 'const volatile unsigned long *addr' cast to 'unsigned long *'
with subsequent unconditional jump to pause (and not to the test) leading
to hang.
Compiling with gcc-4.3 or disabling CONFIG_OPTIMIZE_INLINING yields inlined
constant_test_bit() and correct jump, thus working around the kernel bug.
Other arches than asm-x86 may implement this slightly differently;
2.6.29 mitigates the misoptimization by changing the function prototype
(commit c4295fbb6048d85f0b41c5ced5cbf63f6811c46c) but probably fixing the issue
itself is better.
Signed-off-by: Alexander Chumachenko <ledest@gmail.com>
Signed-off-by: Michael Shigorin <mike@osdn.org.ua>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'CREDITS')
0 files changed, 0 insertions, 0 deletions