+2016-12-20 Stefan Liebler <stli@linux.vnet.ibm.com>
+
+ * sysdeps/unix/sysv/linux/s390/htm.h(__libc_tbegin_retry): New macro.
+ * sysdeps/unix/sysv/linux/s390/elision-lock.c (__lll_lock_elision):
+ Use __libc_tbegin_retry macro.
+
2016-12-20 Stefan Liebler <stli@linux.vnet.ibm.com>
* sysdeps/unix/sysv/linux/s390/Makefile (elision-CFLAGS):
goto use_lock;
}
- int try_tbegin;
- for (try_tbegin = aconf.try_tbegin;
- try_tbegin > 0;
- try_tbegin--)
+ if (aconf.try_tbegin > 0)
{
- int status;
- if (__builtin_expect
- ((status = __libc_tbegin ((void *) 0)) == _HTM_TBEGIN_STARTED, 1))
+ int status = __libc_tbegin_retry ((void *) 0, aconf.try_tbegin - 1);
+ if (__builtin_expect (status == _HTM_TBEGIN_STARTED,
+ _HTM_TBEGIN_STARTED))
{
- if (*futex == 0)
+ if (__builtin_expect (*futex == 0, 1))
+ /* Lock was free. Return to user code in a transaction. */
return 0;
+
/* Lock was busy. Fall back to normal locking. */
if (__builtin_expect (__libc_tx_nesting_depth (), 1))
{
See above for why relaxed MO is sufficient. */
if (aconf.skip_lock_busy > 0)
atomic_store_relaxed (adapt_count, aconf.skip_lock_busy);
- goto use_lock;
}
else /* nesting depth is > 1 */
{
__libc_tabort (_HTM_FIRST_USER_ABORT_CODE | 1);
}
}
+ else if (status != _HTM_TBEGIN_TRANSIENT)
+ {
+ /* A persistent abort (cc 1 or 3) indicates that a retry is
+ probably futile. Use the normal locking now and for the
+ next couple of calls.
+ Be careful to avoid writing to the lock. See above for why
+ relaxed MO is sufficient. */
+ if (aconf.skip_lock_internal_abort > 0)
+ atomic_store_relaxed (adapt_count,
+ aconf.skip_lock_internal_abort);
+ }
else
{
- if (status != _HTM_TBEGIN_TRANSIENT)
- {
- /* A persistent abort (cc 1 or 3) indicates that a retry is
- probably futile. Use the normal locking now and for the
- next couple of calls.
- Be careful to avoid writing to the lock. See above for why
- relaxed MO is sufficient. */
- if (aconf.skip_lock_internal_abort > 0)
- atomic_store_relaxed (adapt_count,
- aconf.skip_lock_internal_abort);
- goto use_lock;
- }
+ /* Same logic as above, but for for a number of temporary failures in
+ a row. */
+ if (aconf.skip_lock_out_of_tbegin_retries > 0)
+ atomic_store_relaxed (adapt_count,
+ aconf.skip_lock_out_of_tbegin_retries);
}
}
- /* Same logic as above, but for for a number of temporary failures in a
- row. See above for why relaxed MO is sufficient. */
- if (aconf.skip_lock_out_of_tbegin_retries > 0 && aconf.try_tbegin > 0)
- atomic_store_relaxed (adapt_count, aconf.skip_lock_out_of_tbegin_retries);
-
use_lock:
+ /* Use normal locking as fallback path if transaction does not succeed. */
return LLL_LOCK ((*futex), private);
}
started. Thus the user of the tbegin macros in this header file has to
compile the file / function with -msoft-float. It prevents gcc from using
fprs / vrs. */
-#define __libc_tbegin(tdb) \
+#define __libc_tbegin(tdb) __libc_tbegin_base(tdb,,,)
+
+#define __libc_tbegin_retry_output_regs , [R_TX_CNT] "+&d" (__tx_cnt)
+#define __libc_tbegin_retry_input_regs(retry_cnt) , [R_RETRY] "d" (retry_cnt)
+#define __libc_tbegin_retry_abort_path_insn \
+ /* If tbegin returned _HTM_TBEGIN_TRANSIENT, retry immediately so \
+ that max tbegin_cnt transactions are tried. Otherwise return and \
+ let the caller of this macro do the fallback path. */ \
+ " jnh 1f\n\t" /* cc 1/3: jump to fallback path. */ \
+ /* tbegin returned _HTM_TBEGIN_TRANSIENT: retry with transaction. */ \
+ " crje %[R_TX_CNT], %[R_RETRY], 1f\n\t" /* Reached max retries? */ \
+ " ahi %[R_TX_CNT], 1\n\t" \
+ " ppa %[R_TX_CNT], 0, 1\n\t" /* Transaction-Abort Assist. */ \
+ " j 2b\n\t" /* Loop to tbegin. */
+
+/* Same as __libc_tbegin except if tbegin aborts with _HTM_TBEGIN_TRANSIENT.
+ Then this macros restores the fpc, fprs and automatically retries up to
+ retry_cnt tbegins. Further saving of the state is omitted as it is already
+ saved. This macro calls tbegin at most as retry_cnt + 1 times. */
+#define __libc_tbegin_retry(tdb, retry_cnt) \
+ ({ int __ret; \
+ int __tx_cnt = 0; \
+ __ret = __libc_tbegin_base(tdb, \
+ __libc_tbegin_retry_abort_path_insn, \
+ __libc_tbegin_retry_output_regs, \
+ __libc_tbegin_retry_input_regs(retry_cnt)); \
+ __ret; \
+ })
+
+#define __libc_tbegin_base(tdb, abort_path_insn, output_regs, input_regs) \
({ int __ret; \
int __fpc; \
char __fprs[TX_FPRS_BYTES]; \
again and result in a core dump wich does \
now show at tbegin but the real executed \
instruction. */ \
- " tbegin 0, 0xFF0E\n\t" \
+ "2: tbegin 0, 0xFF0E\n\t" \
/* Branch away in abort case (this is the \
prefered sequence. See PoP in chapter 5 \
Transactional-Execution Facility \
" srl %[R_RET], 28\n\t" \
" sfpc %[R_FPC]\n\t" \
TX_RESTORE_FPRS \
+ abort_path_insn \
"1:\n\t" \
".machine pop\n" \
: [R_RET] "=&d" (__ret), \
[R_FPC] "=&d" (__fpc) \
+ output_regs \
: [R_FPRS] "a" (__fprs) \
+ input_regs \
: "cc", "memory"); \
__ret; \
})
git://sourceware.org / glibc.git / commitdiff