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 <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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 <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Matt Turner <mattst88@gmail.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Acked-by: David Miller <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
LKML-Reference: <20110126195833.771812729@linutronix.de>
All rwsem implementations include the same headers. Include them from
include/linux/rwsem.h
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Matt Turner <mattst88@gmail.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Acked-by: David Miller <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
LKML-Reference: <20110126195833.483520950@linutronix.de>
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 <behlendorf1@llnl.gov>
Cc: Ben Woodard <bwoodard@llnl.gov>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
FASTCALL() is always expanded to empty, remove it.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Name some of the remaning 'old_style_spin_init' locks
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Use the lock validator framework to prove rwsem locking correctness.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add sem_is_read/write_locked functions to the read/write semaphores, along the
same lines of the *_is_locked spinlock functions. The swap token tuning patch
uses sem_is_read_locked; sem_is_write_locked is added for completeness.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Thomas Gleixner