[PATCH 4/4] S390: Optimize lock-elision by decrementing adapt_count at unlock.

[Stefan Liebler]

On 01/18/2017 05:25 PM, Torvald Riegel wrote:
> On Wed, 2017-01-18 at 13:28 +0100, Stefan Liebler wrote:
>> On 01/17/2017 07:52 PM, Torvald Riegel wrote:
>>> On Tue, 2017-01-17 at 16:28 +0100, Stefan Liebler wrote:
>>> The rest of the diff looked OK.
>>>
>> If it's okay, I will make one patch with all the reviewed diffs and post
>> it with a ChangeLog in this mail-thread.
>> Then I would commit it before release to have a consistent state?
>
> Yes, please commit this.
>
>
>
Okay. I'll commit this patch.
Thanks.

S390: Adjust lock elision code after review.

This patch adjusts s390 specific lock elision code after review
of the following patches:
-S390: Use own tbegin macro instead of __builtin_tbegin.
(8bfc4a2ab4bebdf86c151665aae8a266e2f18fb4)
-S390: Use new __libc_tbegin_retry macro in elision-lock.c.
(53c5c3d5ac238901c13f28a73ba05b0678094e80)
-S390: Optimize lock-elision by decrementing adapt_count at unlock.
(dd037fb3df286b7c2d0b0c6f8d02a2dd8a8e8a08)

The futex value is not tested before starting a transaction,
__glibc_likely is used instead of __builtin_expect and comments
are adjusted.

ChangeLog:

	* sysdeps/unix/sysv/linux/s390/htm.h: Adjust comments.
	* sysdeps/unix/sysv/linux/s390/elision-unlock.c: Likewise.
	* sysdeps/unix/sysv/linux/s390/elision-lock.c: Adjust comments.
	(__lll_lock_elision): Do not test futex before starting a
	transaction.  Use __glibc_likely instead of __builtin_expect.
	* sysdeps/unix/sysv/linux/s390/elision-trylock.c: Adjust comments.
	(__lll_trylock_elision): Do not test futex before starting a
	transaction.  Use __glibc_likely instead of __builtin_expect.
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