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authorPeter Zijlstra <peterz@infradead.org>2015-08-12 21:04:22 +0200
committerIngo Molnar <mingo@kernel.org>2015-08-13 08:44:43 +0200
commitd420acd816c07c7be31bd19d09cbcb16e5572fa6 (patch)
tree4d66213e5f6ee3ad6b4ba769bd595f362273dd4d /scripts
parent0ca326de7aa9cb253db9c1a3eb3f0487c8dbf912 (diff)
downloadlinux-d420acd816c07c7be31bd19d09cbcb16e5572fa6.tar.gz
jump_label/x86: Work around asm build bug on older/backported GCCs
Boris reported that gcc version 4.4.4 20100503 (Red Hat 4.4.4-2) fails to build linux-next kernels that have this fresh commit via the locking tree: 11276d5306b8 ("locking/static_keys: Add a new static_key interface") The problem appears to be that even though @key and @branch are compile time constants, it doesn't see the following expression as an immediate value: &((char *)key)[branch] More recent GCCs don't appear to have this problem. In particular, Red Hat backported the 'asm goto' feature into 4.4, 'normal' 4.4 compilers will not have this feature and thus not run into this asm. The workaround is to supply both values to the asm as immediates and do the addition in asm. Suggested-by: H. Peter Anvin <hpa@zytor.com> Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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