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a9f180345f
I started noticing problems with KVM guest destruction on Linux 3.12+, where guest memory wasn't being cleaned up. I bisected it down to the commit introducing the new 'asm goto'-based atomics, and found this quirk was later applied to those. Unfortunately, even with GCC 4.8.2 (which ostensibly fixed the known 'asm goto' bug) I am still getting some kind of miscompilation. If I enable the asm_volatile_goto quirk for my compiler, KVM guests are destroyed correctly and the memory is cleaned up. So make the quirk unconditional for now, until bug is found and fixed. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Noonan <steven@uplinklabs.net> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jakub Jelinek <jakub@redhat.com> Cc: Richard Henderson <rth@twiddle.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/1392274867-15236-1-git-send-email-steven@uplinklabs.net Link: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 Signed-off-by: Ingo Molnar <mingo@kernel.org>
89 lines
3.0 KiB
C
89 lines
3.0 KiB
C
#ifndef __LINUX_COMPILER_H
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#error "Please don't include <linux/compiler-gcc4.h> directly, include <linux/compiler.h> instead."
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#endif
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/* GCC 4.1.[01] miscompiles __weak */
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#ifdef __KERNEL__
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# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
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# error Your version of gcc miscompiles the __weak directive
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# endif
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#endif
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#define __used __attribute__((__used__))
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#define __must_check __attribute__((warn_unused_result))
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#define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
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#if GCC_VERSION >= 40100 && GCC_VERSION < 40600
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# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
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#endif
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#if GCC_VERSION >= 40300
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/* Mark functions as cold. gcc will assume any path leading to a call
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to them will be unlikely. This means a lot of manual unlikely()s
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are unnecessary now for any paths leading to the usual suspects
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like BUG(), printk(), panic() etc. [but let's keep them for now for
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older compilers]
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Early snapshots of gcc 4.3 don't support this and we can't detect this
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in the preprocessor, but we can live with this because they're unreleased.
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Maketime probing would be overkill here.
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gcc also has a __attribute__((__hot__)) to move hot functions into
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a special section, but I don't see any sense in this right now in
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the kernel context */
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#define __cold __attribute__((__cold__))
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#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
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#ifndef __CHECKER__
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# define __compiletime_warning(message) __attribute__((warning(message)))
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# define __compiletime_error(message) __attribute__((error(message)))
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#endif /* __CHECKER__ */
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#endif /* GCC_VERSION >= 40300 */
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#if GCC_VERSION >= 40500
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/*
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* Mark a position in code as unreachable. This can be used to
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* suppress control flow warnings after asm blocks that transfer
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* control elsewhere.
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*
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* Early snapshots of gcc 4.5 don't support this and we can't detect
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* this in the preprocessor, but we can live with this because they're
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* unreleased. Really, we need to have autoconf for the kernel.
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*/
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#define unreachable() __builtin_unreachable()
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/* Mark a function definition as prohibited from being cloned. */
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#define __noclone __attribute__((__noclone__))
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#endif /* GCC_VERSION >= 40500 */
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#if GCC_VERSION >= 40600
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/*
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* Tell the optimizer that something else uses this function or variable.
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*/
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#define __visible __attribute__((externally_visible))
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#endif
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/*
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* GCC 'asm goto' miscompiles certain code sequences:
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*
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* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
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*
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* Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
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* Fixed in GCC 4.8.2 and later versions.
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*
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* (asm goto is automatically volatile - the naming reflects this.)
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*/
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#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
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#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
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#if GCC_VERSION >= 40400
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#define __HAVE_BUILTIN_BSWAP32__
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#define __HAVE_BUILTIN_BSWAP64__
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#endif
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#if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600)
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#define __HAVE_BUILTIN_BSWAP16__
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#endif
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#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
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