linux.git/include/linux/rwsem-spinlock.h, branch v4.14-rc4

locking/rwsem-spinlock: Add killable versions of __down_read()

2017-08-10T10:28:55+00:00

Rename __down_read() in __down_read_common() and teach it
to abort waiting in case of pending signals and killable
state argument passed.

Note, that we shouldn't wake anybody up in EINTR path, as:

We check for signal_pending_state() after (!waiter.task)
test and under spinlock. So, current task wasn't able to
be woken up. It may be in two cases: a writer is owner
of the sem, or a writer is a first waiter of the sem.

If a writer is owner of the sem, no one else may work
with it in parallel. It will wake somebody, when it
call up_write() or downgrade_write().

If a writer is the first waiter, it will be woken up,
when the last active reader releases the sem, and
sem->count became 0.

Also note, that set_current_state() may be moved down
to schedule() (after !waiter.task check), as all
assignments in this type of semaphore (including wake_up),
occur under spinlock, so we can't miss anything.

Signed-off-by: Kirill Tkhai 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: arnd@arndb.de
Cc: avagin@virtuozzo.com
Cc: davem@davemloft.net
Cc: fenghua.yu@intel.com
Cc: gorcunov@virtuozzo.com
Cc: heiko.carstens@de.ibm.com
Cc: hpa@zytor.com
Cc: ink@jurassic.park.msu.ru
Cc: mattst88@gmail.com
Cc: rth@twiddle.net
Cc: schwidefsky@de.ibm.com
Cc: tony.luck@intel.com
Link: http://lkml.kernel.org/r/149789533283.9059.9829416940494747182.stgit@localhost.localdomain
Signed-off-by: Ingo Molnar

locking/rwsem: Introduce basis for down_write_killable()

2016-04-13T08:42:20+00:00

Introduce a generic implementation necessary for down_write_killable().

This is a trivial extension of the already existing down_write() call
which can be interrupted by SIGKILL.  This patch doesn't provide
down_write_killable() yet because arches have to provide the necessary
pieces before.

rwsem_down_write_failed() which is a generic slow path for the
write lock is extended to take a task state and renamed to
__rwsem_down_write_failed_common(). The return value is either a valid
semaphore pointer or ERR_PTR(-EINTR).

rwsem_down_write_failed_killable() is exported as a new way to wait for
the lock and be killable.

For rwsem-spinlock implementation the current __down_write() it updated
in a similar way as __rwsem_down_write_failed_common() except it doesn't
need new exports just visible __down_write_killable().

Architectures which are not using the generic rwsem implementation are
supposed to provide their __down_write_killable() implementation and
use rwsem_down_write_failed_killable() for the slow path.

Signed-off-by: Michal Hocko 
Cc: Andrew Morton 
Cc: Chris Zankel 
Cc: David S. Miller 
Cc: Linus Torvalds 
Cc: Max Filippov 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Signed-off-by: Davidlohr Bueso 
Cc: Signed-off-by: Jason Low 
Cc: Thomas Gleixner 
Cc: Tony Luck 
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/1460041951-22347-7-git-send-email-mhocko@kernel.org
Signed-off-by: Ingo Molnar

locking/rwsem: Get rid of __down_write_nested()

2016-04-13T08:42:16+00:00

This is no longer used anywhere and all callers (__down_write()) use
0 as a subclass. Ditch __down_write_nested() to make the code easier
to follow.

This shouldn't introduce any functional change.

Signed-off-by: Michal Hocko 
Acked-by: Davidlohr Bueso 
Cc: Andrew Morton 
Cc: Chris Zankel 
Cc: David S. Miller 
Cc: Linus Torvalds 
Cc: Max Filippov 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Signed-off-by: Davidlohr Bueso 
Cc: Signed-off-by: Jason Low 
Cc: Thomas Gleixner 
Cc: Tony Luck 
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/1460041951-22347-2-git-send-email-mhocko@kernel.org
Signed-off-by: Ingo Molnar

locking/rwsem: Rename 'activity' to 'count'

2014-07-16T12:56:55+00:00

There are two definitions of struct rw_semaphore, one in linux/rwsem.h
and one in linux/rwsem-spinlock.h.

For some reason they have different names for the initial field. This
makes it impossible to use C99 named initialization for
__RWSEM_INITIALIZER() -- or we have to duplicate that entire thing
along with the structure definitions.

The simpler patch is renaming the rwsem-spinlock variant to match the
regular rwsem.

This allows us to switch to C99 named initialization.

Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/n/tip-bmrZolsbGmautmzrerog27io@git.kernel.org
Signed-off-by: Ingo Molnar

locking, rwsem: Annotate inner lock as raw

2011-09-13T09:11:59+00:00

There is no reason to allow the lock protecting rwsems (the
ownerless variant) to be preemptible on -rt. Convert it to raw.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Ingo Molnar

rwsem: Move duplicate init macros and functions to linux/rwsem.h

2011-01-27T11:30:39+00:00

The rwsem initializers and related macros and functions are mostly the
same. Some of them lack the lockdep initializer, but having it in
place does not matter for architectures which do not support lockdep.

powerpc, sparc, x86: No functional change

sh, s390: Removes the duplicate init_rwsem (inline and #define)

alpha, ia64, xtensa: Use the lockdep capable init function in
       	     	     lib/rwsem.c which is just uninlining the init
       	     	     function for the LOCKDEP=n case

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: David Howells 
Cc: Benjamin Herrenschmidt 
Cc: Matt Turner 
Acked-by: Tony Luck 
Acked-by: Heiko Carstens 
Cc: Paul Mundt 
Acked-by: David Miller 
Cc: Chris Zankel 
LKML-Reference: <20110126195833.771812729@linutronix.de>

rwsem: Cleanup includes

2011-01-27T11:30:38+00:00

All rwsem implementations include the same headers. Include them from
include/linux/rwsem.h

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: David Howells 
Cc: Benjamin Herrenschmidt 
Cc: Matt Turner 
Acked-by: Tony Luck 
Acked-by: Heiko Carstens 
Cc: Paul Mundt 
Acked-by: David Miller 
Cc: Chris Zankel 
LKML-Reference: <20110126195833.483520950@linutronix.de>

rwsem: fix rwsem_is_locked() bugs

2009-12-15T16:53:26+00:00

rwsem_is_locked() tests ->activity without locks, so we should always keep
->activity consistent.  However, the code in __rwsem_do_wake() breaks this
rule, it updates ->activity after _all_ readers waken up, this may give
some reader a wrong ->activity value, thus cause rwsem_is_locked() behaves
wrong.

Quote from Andrew:

"
- we have one or more processes sleeping in down_read(), waiting for access.

- we wake one or more processes up without altering ->activity

- they start to run and they do rwsem_is_locked().  This incorrectly
  returns "false", because the waker process is still crunching away in
  __rwsem_do_wake().

- the waker now alters ->activity, but it was too late.
"

So we need get a spinlock to protect this.  And rwsem_is_locked() should
not block, thus we use spin_trylock_irqsave().

[akpm@linux-foundation.org: simplify code]
Reported-by: Brian Behlendorf 
Cc: Ben Woodard 
Cc: David Howells 
Signed-off-by: WANG Cong 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

include/linux: Remove all users of FASTCALL() macro

2008-02-14T00:21:18+00:00

FASTCALL() is always expanded to empty, remove it.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Harvey Harrison 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] lockdep: name some old style locks

2006-12-07T16:39:36+00:00

Name some of the remaning 'old_style_spin_init' locks

Signed-off-by: Peter Zijlstra 
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds