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S390: Use new __libc_tbegin_retry macro in elision-lock.c.

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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
2016-12-20 15:12:48 +01:00
parent 8bfc4a2ab4
commit 53c5c3d5ac
3 changed files with 64 additions and 28 deletions
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6
ChangeLog
View File

@@ -1,3 +1,9 @@
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):

36
sysdeps/unix/sysv/linux/s390/elision-lock.c
View File

@@ -60,17 +60,16 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
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))
{
@@ -81,7 +80,6 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
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 */
{
@@ -99,9 +97,7 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
__libc_tabort (_HTM_FIRST_USER_ABORT_CODE | 1);
}
}
else
{
if (status != _HTM_TBEGIN_TRANSIENT)
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
@@ -111,16 +107,18 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
if (aconf.skip_lock_internal_abort > 0)
atomic_store_relaxed (adapt_count,
aconf.skip_lock_internal_abort);
goto use_lock;
}
else
{
/* 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);
}

36
sysdeps/unix/sysv/linux/s390/htm.h
View File

@@ -69,7 +69,36 @@
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]; \
@@ -95,7 +124,7 @@
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 \
@@ -111,11 +140,14 @@
" 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; \
})