Introduce for this operation the reverse NO_ADAPTIVE_SX option.
The flag SX_ADAPTIVESPIN to be passed to sx_init_flags(9) gets suppressed
and the new flag, offering the reversed logic, SX_NOADAPTIVE is added.
Additively implements adaptive spininning for sx held in shared mode.
The spinning limit can be handled through sysctls in order to be tuned
while the code doesn't reach the release, after which time they should
be dropped probabilly.
This change has made been necessary by recent benchmarks where it does
improve concurrency of workloads in presence of high contention
(ie. ZFS).
KPI breakage is documented by __FreeBSD_version bumping, manpage and
UPDATING updates.
Requested by: jeff, kmacy
Reviewed by: jeff
Tested by: pho
obtaining and releasing shared and exclusive locks. The algorithms for
manipulating the lock cookie are very similar to that rwlocks. This patch
also adds support for exclusive locks using the same algorithm as mutexes.
A new sx_init_flags() function has been added so that optional flags can be
specified to alter a given locks behavior. The flags include SX_DUPOK,
SX_NOWITNESS, SX_NOPROFILE, and SX_QUITE which are all identical in nature
to the similar flags for mutexes.
Adaptive spinning on select locks may be enabled by enabling the
ADAPTIVE_SX kernel option. Only locks initialized with the SX_ADAPTIVESPIN
flag via sx_init_flags() will adaptively spin.
The common cases for sx_slock(), sx_sunlock(), sx_xlock(), and sx_xunlock()
are now performed inline in non-debug kernels. As a result, <sys/sx.h> now
requires <sys/lock.h> to be included prior to <sys/sx.h>.
The new kernel option SX_NOINLINE can be used to disable the aforementioned
inlining in non-debug kernels.
The size of struct sx has changed, so the kernel ABI is probably greatly
disturbed.
MFC after: 1 month
Submitted by: attilio
Tested by: kris, pjd
event. Locking primitives that support this (mtx, rw, and sx) now each
include their own foo_sleep() routine.
- Rename msleep() to _sleep() and change it's 'struct mtx' object to a
'struct lock_object' pointer. _sleep() uses the recently added
lc_unlock() and lc_lock() function pointers for the lock class of the
specified lock to release the lock while the thread is suspended.
- Add wrappers around _sleep() for mutexes (mtx_sleep()), rw locks
(rw_sleep()), and sx locks (sx_sleep()). msleep() still exists and
is now identical to mtx_sleep(), but it is deprecated.
- Rename SLEEPQ_MSLEEP to SLEEPQ_SLEEP.
- Rewrite much of sleep.9 to not be msleep(9) centric.
- Flesh out the 'RETURN VALUES' section in sleep.9 and add an 'ERRORS'
section.
- Add __nonnull(1) to _sleep() and msleep_spin() so that the compiler will
warn if you try to pass a NULL wait channel. The functions already have
a KASSERT to that effect.
- Markup sx_unlock() as a function rather than saying it is a macro.
The macro part is an implementation detail, and all the other sx_*lock()
functions are actually macros, too.
- Use the same style as rwlock(9) and mutex(9) to markup sx_assert() and
SX_SYSINIT() with respect to headers and kernel options.
- Add a missing MLINK.
a single lock at the same time.
- Avoid using "own" to refer to holding either a shared or exclusive lock
as it is only really correct for exclusive locks.
- Reword the sentence about sleep-ability to read easier.
Requested by: truckman (1)
PS. There is a inconsistency in this manual page, because in
non-WITNESS case sx_assert(9) does not panics, it only prints
the warning. I haven't fixed this, because jhb@ is planing to
replace those printf()s with panic()s.
Reviewed by: jhb
Approved by: jhb, scottl (mentor)
- A #include of <sys/mutex.h> is no longer needed to use sx(9) (since
2001/05/01).
- Use of the SX_SYSINIT() macro requires inclusion of '<sys/kernel.h>'
cd src/share; find man[1-9] -type f|xargs perl -pi -e 's/[ \t]+$//'
BTW, what editors are the culprits? I'm using vim and it shows
me whitespace at EOL in troff files with a thick blue block...
Reviewed by: Silence from cvs diff -b
MFC after: 7 days
