From feba40362b11341bee6d8ed58d54b896abbd9f84 Mon Sep 17 00:00:00 2001 From: Sam bobroff Date: Fri, 10 Apr 2015 14:16:47 +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 immediately without performing the syscall. 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 because syscalls will still be performed after tsuspend. 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 system call increases by about 0.5%. Signed-off-by: Sam Bobroff Acked-By: Michael Neuling Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/entry_64.S | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'arch/powerpc/kernel') diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index afbc20019c2e..8ca9434c40e6 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -34,6 +34,7 @@ #include #include #include +#include /* * System calls. @@ -145,6 +146,24 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR) andi. r11,r10,_TIF_SYSCALL_DOTRACE bne syscall_dotrace .Lsyscall_dotrace_cont: +#ifdef CONFIG_PPC_TRANSACTIONAL_MEM +BEGIN_FTR_SECTION + b 1f +END_FTR_SECTION_IFCLR(CPU_FTR_TM) + extrdi. r11, r12, 1, (63-MSR_TS_T_LG) /* transaction active? */ + beq+ 1f + + /* Doom the transaction and don't perform the syscall: */ + mfmsr r11 + li r12, 1 + rldimi r11, r12, MSR_TM_LG, 63-MSR_TM_LG + mtmsrd r11, 0 + li r11, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) + TABORT(R11) + + b .Lsyscall_exit +1: +#endif cmpldi 0,r0,NR_syscalls bge- syscall_enosys -- cgit v1.2.3