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S390: Use new __libc_tbegin_retry macro in elision-lock.c.
This patch implements __libc_tbegin_retry macro which is equivalent to gcc builtin __builtin_tbegin_retry, except the changes which were applied to __libc_tbegin in the previous patch. 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 in the first round. Before retrying a further transaction, the transaction-abort-assist instruction is used to support the cpu. This macro is now used in function __lll_lock_elision. ChangeLog: * 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.
This commit is contained in:
Stefan Liebler
parent
8bfc4a2ab4
commit
53c5c3d5ac
@ -1,3 +1,9 @@
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2016-12-20 Stefan Liebler <stli@linux.vnet.ibm.com>
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* sysdeps/unix/sysv/linux/s390/htm.h(__libc_tbegin_retry): New macro.
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* sysdeps/unix/sysv/linux/s390/elision-lock.c (__lll_lock_elision):
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Use __libc_tbegin_retry macro.
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2016-12-20 Stefan Liebler <stli@linux.vnet.ibm.com>
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* sysdeps/unix/sysv/linux/s390/Makefile (elision-CFLAGS):
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@ -60,17 +60,16 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
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goto use_lock;
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}
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int try_tbegin;
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for (try_tbegin = aconf.try_tbegin;
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try_tbegin > 0;
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try_tbegin--)
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if (aconf.try_tbegin > 0)
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{
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int status;
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if (__builtin_expect
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((status = __libc_tbegin ((void *) 0)) == _HTM_TBEGIN_STARTED, 1))
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int status = __libc_tbegin_retry ((void *) 0, aconf.try_tbegin - 1);
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if (__builtin_expect (status == _HTM_TBEGIN_STARTED,
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_HTM_TBEGIN_STARTED))
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{
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if (*futex == 0)
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if (__builtin_expect (*futex == 0, 1))
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/* Lock was free. Return to user code in a transaction. */
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return 0;
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/* Lock was busy. Fall back to normal locking. */
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if (__builtin_expect (__libc_tx_nesting_depth (), 1))
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{
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@ -81,7 +80,6 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
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See above for why relaxed MO is sufficient. */
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if (aconf.skip_lock_busy > 0)
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atomic_store_relaxed (adapt_count, aconf.skip_lock_busy);
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goto use_lock;
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}
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else /* nesting depth is > 1 */
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{
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@ -99,28 +97,28 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
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__libc_tabort (_HTM_FIRST_USER_ABORT_CODE | 1);
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}
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}
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else if (status != _HTM_TBEGIN_TRANSIENT)
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{
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/* A persistent abort (cc 1 or 3) indicates that a retry is
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probably futile. Use the normal locking now and for the
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next couple of calls.
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Be careful to avoid writing to the lock. See above for why
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relaxed MO is sufficient. */
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if (aconf.skip_lock_internal_abort > 0)
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atomic_store_relaxed (adapt_count,
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aconf.skip_lock_internal_abort);
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}
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else
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{
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if (status != _HTM_TBEGIN_TRANSIENT)
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{
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/* A persistent abort (cc 1 or 3) indicates that a retry is
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probably futile. Use the normal locking now and for the
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next couple of calls.
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Be careful to avoid writing to the lock. See above for why
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relaxed MO is sufficient. */
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if (aconf.skip_lock_internal_abort > 0)
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atomic_store_relaxed (adapt_count,
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aconf.skip_lock_internal_abort);
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goto use_lock;
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}
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/* Same logic as above, but for for a number of temporary failures in
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a row. */
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if (aconf.skip_lock_out_of_tbegin_retries > 0)
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atomic_store_relaxed (adapt_count,
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aconf.skip_lock_out_of_tbegin_retries);
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}
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}
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/* Same logic as above, but for for a number of temporary failures in a
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row. See above for why relaxed MO is sufficient. */
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if (aconf.skip_lock_out_of_tbegin_retries > 0 && aconf.try_tbegin > 0)
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atomic_store_relaxed (adapt_count, aconf.skip_lock_out_of_tbegin_retries);
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use_lock:
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/* Use normal locking as fallback path if transaction does not succeed. */
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return LLL_LOCK ((*futex), private);
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}
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@ -69,7 +69,36 @@
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started. Thus the user of the tbegin macros in this header file has to
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compile the file / function with -msoft-float. It prevents gcc from using
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fprs / vrs. */
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#define __libc_tbegin(tdb) \
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#define __libc_tbegin(tdb) __libc_tbegin_base(tdb,,,)
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#define __libc_tbegin_retry_output_regs , [R_TX_CNT] "+&d" (__tx_cnt)
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#define __libc_tbegin_retry_input_regs(retry_cnt) , [R_RETRY] "d" (retry_cnt)
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#define __libc_tbegin_retry_abort_path_insn \
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/* If tbegin returned _HTM_TBEGIN_TRANSIENT, retry immediately so \
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that max tbegin_cnt transactions are tried. Otherwise return and \
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let the caller of this macro do the fallback path. */ \
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" jnh 1f\n\t" /* cc 1/3: jump to fallback path. */ \
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/* tbegin returned _HTM_TBEGIN_TRANSIENT: retry with transaction. */ \
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" crje %[R_TX_CNT], %[R_RETRY], 1f\n\t" /* Reached max retries? */ \
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" ahi %[R_TX_CNT], 1\n\t" \
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" ppa %[R_TX_CNT], 0, 1\n\t" /* Transaction-Abort Assist. */ \
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" j 2b\n\t" /* Loop to tbegin. */
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/* Same as __libc_tbegin except if tbegin aborts with _HTM_TBEGIN_TRANSIENT.
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Then this macros restores the fpc, fprs and automatically retries up to
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retry_cnt tbegins. Further saving of the state is omitted as it is already
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saved. This macro calls tbegin at most as retry_cnt + 1 times. */
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#define __libc_tbegin_retry(tdb, retry_cnt) \
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({ int __ret; \
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int __tx_cnt = 0; \
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__ret = __libc_tbegin_base(tdb, \
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__libc_tbegin_retry_abort_path_insn, \
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__libc_tbegin_retry_output_regs, \
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__libc_tbegin_retry_input_regs(retry_cnt)); \
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__ret; \
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})
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#define __libc_tbegin_base(tdb, abort_path_insn, output_regs, input_regs) \
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({ int __ret; \
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int __fpc; \
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char __fprs[TX_FPRS_BYTES]; \
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@ -95,7 +124,7 @@
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again and result in a core dump wich does \
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now show at tbegin but the real executed \
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instruction. */ \
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" tbegin 0, 0xFF0E\n\t" \
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"2: tbegin 0, 0xFF0E\n\t" \
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/* Branch away in abort case (this is the \
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prefered sequence. See PoP in chapter 5 \
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Transactional-Execution Facility \
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@ -111,11 +140,14 @@
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" srl %[R_RET], 28\n\t" \
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" sfpc %[R_FPC]\n\t" \
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TX_RESTORE_FPRS \
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abort_path_insn \
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"1:\n\t" \
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".machine pop\n" \
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: [R_RET] "=&d" (__ret), \
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[R_FPC] "=&d" (__fpc) \
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output_regs \
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: [R_FPRS] "a" (__fprs) \
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input_regs \
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: "cc", "memory"); \
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__ret; \
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})
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