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| author | Alexander Chumachenko <[email protected]> | 2010-04-01 12:34:52 +0000 |
|---|---|---|
| committer | H. Peter Anvin <[email protected]> | 2010-09-27 05:43:07 +0000 |
| commit | c9e2fbd909c20b165b2b9ffb59f8b674cf0a55b0 (patch) | |
| tree | 29b4f977e3a1fa4b0b85057c35652ee5fe58949e /tools/perf/scripts/python/check-perf-trace.py | |
| parent | Merge branch 'amd-iommu/2.6.36' of git://git.kernel.org/pub/scm/linux/kernel/... (diff) | |
| download | kernel-c9e2fbd909c20b165b2b9ffb59f8b674cf0a55b0.tar.gz kernel-c9e2fbd909c20b165b2b9ffb59f8b674cf0a55b0.zip | |
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 <[email protected]>
Signed-off-by: Michael Shigorin <[email protected]>
Acked-by: Linus Torvalds <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Diffstat (limited to 'tools/perf/scripts/python/check-perf-trace.py')
0 files changed, 0 insertions, 0 deletions