diff options
| -rw-r--r-- | Documentation/powerpc/transactional_memory.txt | 32 | ||||
| -rw-r--r-- | arch/powerpc/include/uapi/asm/tm.h | 2 | ||||
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 19 |
3 files changed, 36 insertions, 17 deletions
diff --git a/Documentation/powerpc/transactional_memory.txt b/Documentation/powerpc/transactional_memory.txt index 9791e98ab49c..98b39af5254f 100644 --- a/Documentation/powerpc/transactional_memory.txt +++ b/Documentation/powerpc/transactional_memory.txt @@ -74,22 +74,23 @@ Causes of transaction aborts Syscalls ======== -Performing syscalls from within transaction is not recommended, and can lead -to unpredictable results. +Syscalls made from within an active transaction will not be performed and the +transaction will be doomed by the kernel with the failure code TM_CAUSE_SYSCALL +| TM_CAUSE_PERSISTENT. -Syscalls do not by design abort transactions, but beware: The kernel code will -not be running in transactional state. The effect of syscalls will always -remain visible, but depending on the call they may abort your transaction as a -side-effect, read soon-to-be-aborted transactional data that should not remain -invisible, etc. If you constantly retry a transaction that constantly aborts -itself by calling a syscall, you'll have a livelock & make no progress. +Syscalls made from within a suspended transaction are performed as normal and +the transaction is not explicitly doomed by the kernel. However, what the +kernel does to perform the syscall may result in the transaction being doomed +by the hardware. The syscall is performed in suspended mode so any side +effects will be persistent, independent of transaction success or failure. No +guarantees are provided by the kernel about which syscalls will affect +transaction success. -Simple syscalls (e.g. sigprocmask()) "could" be OK. Even things like write() -from, say, printf() should be OK as long as the kernel does not access any -memory that was accessed transactionally. - -Consider any syscalls that happen to work as debug-only -- not recommended for -production use. Best to queue them up till after the transaction is over. +Care must be taken when relying on syscalls to abort during active transactions +if the calls are made via a library. Libraries may cache values (which may +give the appearance of success) or perform operations that cause transaction +failure before entering the kernel (which may produce different failure codes). +Examples are glibc's getpid() and lazy symbol resolution. Signals @@ -176,8 +177,7 @@ kernel aborted a transaction: TM_CAUSE_RESCHED Thread was rescheduled. TM_CAUSE_TLBI Software TLB invalide. TM_CAUSE_FAC_UNAV FP/VEC/VSX unavailable trap. - TM_CAUSE_SYSCALL Currently unused; future syscalls that must abort - transactions for consistency will use this. + TM_CAUSE_SYSCALL Syscall from active transaction. TM_CAUSE_SIGNAL Signal delivered. TM_CAUSE_MISC Currently unused. TM_CAUSE_ALIGNMENT Alignment fault. 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 |