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authorSam bobroff <sam.bobroff@au1.ibm.com>2015-04-10 14:16:47 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2015-04-11 20:49:19 +1000
commitfeba40362b11341bee6d8ed58d54b896abbd9f84 (patch)
tree1260122ddfe4ae26ad224367097e2ca38fc8c6be /arch/powerpc
parent771e569e8200ab6f5cdbcd6513f7a476718bb44d (diff)
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 <sam.bobroff@au1.ibm.com> Acked-By: Michael Neuling <mikey@neuling.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/include/uapi/asm/tm.h2
-rw-r--r--arch/powerpc/kernel/entry_64.S19
2 files changed, 20 insertions, 1 deletions
diff --git a/arch/powerpc/include/uapi/asm/tm.h b/arch/powerpc/include/uapi/asm/tm.h
index 5d836b7c1176..5047659815a5 100644
--- a/arch/powerpc/include/uapi/asm/tm.h
+++ b/arch/powerpc/include/uapi/asm/tm.h
@@ -11,7 +11,7 @@
#define TM_CAUSE_RESCHED 0xde
#define TM_CAUSE_TLBI 0xdc
#define TM_CAUSE_FAC_UNAV 0xda
-#define TM_CAUSE_SYSCALL 0xd8 /* future use */
+#define TM_CAUSE_SYSCALL 0xd8
#define TM_CAUSE_MISC 0xd6 /* future use */
#define TM_CAUSE_SIGNAL 0xd4
#define TM_CAUSE_ALIGNMENT 0xd2
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 <asm/ftrace.h>
#include <asm/hw_irq.h>
#include <asm/context_tracking.h>
+#include <asm/tm.h>
/*
* 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