From b4b56f9ecab40f3b4ef53e130c9f6663be491894 Mon Sep 17 00:00:00 2001 From: Sam bobroff Date: Fri, 12 Jun 2015 11:06:32 +1000 Subject: powerpc/tm: Abort syscalls in active transactions This patch changes the syscall handler to doom (tabort) active transactions when a syscall is made and return very early without performing the syscall and keeping side effects to a minimum (no CPU accounting or system call tracing is performed). Also included is a new HWCAP2 bit, PPC_FEATURE2_HTM_NOSC, to indicate this behaviour to userspace. Currently, the system call instruction automatically suspends an active transaction which causes side effects to persist when an active transaction fails. This does change the kernel's behaviour, but in a way that was documented as unsupported. It doesn't reduce functionality as syscalls will still be performed after tsuspend; it just requires that the transaction be explicitly suspended. It also provides a consistent interface and makes the behaviour of user code substantially the same across powerpc and platforms that do not support suspended transactions (e.g. x86 and s390). Performance measurements using http://ozlabs.org/~anton/junkcode/null_syscall.c indicate the cost of a normal (non-aborted) system call increases by about 0.25%. Signed-off-by: Sam Bobroff Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/cputable.h | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'arch/powerpc/include/asm/cputable.h') diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h index 6367b8347dad..4994648b9265 100644 --- a/arch/powerpc/include/asm/cputable.h +++ b/arch/powerpc/include/asm/cputable.h @@ -242,11 +242,13 @@ enum { /* We only set the TM feature if the kernel was compiled with TM supprt */ #ifdef CONFIG_PPC_TRANSACTIONAL_MEM -#define CPU_FTR_TM_COMP CPU_FTR_TM -#define PPC_FEATURE2_HTM_COMP PPC_FEATURE2_HTM +#define CPU_FTR_TM_COMP CPU_FTR_TM +#define PPC_FEATURE2_HTM_COMP PPC_FEATURE2_HTM +#define PPC_FEATURE2_HTM_NOSC_COMP PPC_FEATURE2_HTM_NOSC #else -#define CPU_FTR_TM_COMP 0 -#define PPC_FEATURE2_HTM_COMP 0 +#define CPU_FTR_TM_COMP 0 +#define PPC_FEATURE2_HTM_COMP 0 +#define PPC_FEATURE2_HTM_NOSC_COMP 0 #endif /* We need to mark all pages as being coherent if we're SMP or we have a -- cgit v1.2.3