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* rwsem: simplify __rwsem_do_wakeMichel Lespinasse2013-05-071-16/+7
| | | | | | | | | | | | | | | | | This is mostly for cleanup value: - We don't need several gotos to handle the case where the first waiter is a writer. Two simple tests will do (and generate very similar code). - In the remainder of the function, we know the first waiter is a reader, so we don't have to double check that. We can use do..while loops to iterate over the readers to wake (generates slightly better code). Signed-off-by: Michel Lespinasse <walken@google.com> Reviewed-by: Peter Hurley <peter@hurleysoftware.com> Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* rwsem: make the waiter type an enumeration rather than a bitmaskMichel Lespinasse2013-05-071-8/+11
| | | | | | | | | | | | | | | We are not planning to add some new waiter flags, so we can convert the waiter type into an enumeration. Background: David Howells suggested I do this back when I tried adding a new waiter type for unfair readers. However, I believe the cleanup applies regardless of that use case. Signed-off-by: Michel Lespinasse <walken@google.com> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Peter Hurley <peter@hurleysoftware.com> Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* rwsem-spinlock: Implement writer lock-stealing for better scalabilityYuanhan Liu2013-02-191-45/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We (Linux Kernel Performance project) found a regression introduced by commit: 5a505085f043 mm/rmap: Convert the struct anon_vma::mutex to an rwsem which converted all anon_vma::mutex locks rwsem write locks. The semantics are the same, but the behavioral difference is quite huge in some cases. After investigating it we found the root cause: mutexes support lock stealing while rwsems don't. Here is the link for the detailed regression report: https://lkml.org/lkml/2013/1/29/84 Ingo suggested adding write lock stealing to rwsems: "I think we should allow lock-steal between rwsem writers - that will not hurt fairness as most rwsem fairness concerns relate to reader vs. writer fairness" And here is the rwsem-spinlock version. With this patch, we got a double performance increase in one test box with following aim7 workfile: FILESIZE: 1M POOLSIZE: 10M 10 fork_test /usr/bin/time output w/o patch /usr/bin/time_output with patch -- Percent of CPU this job got: 369% Percent of CPU this job got: 537% Voluntary context switches: 640595016 Voluntary context switches: 157915561 We got a 45% increase in CPU usage and saved about 3/4 voluntary context switches. Reported-by: LKP project <lkp@linux.intel.com> Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Alex Shi <alex.shi@intel.com> Cc: David Howells <dhowells@redhat.com> Cc: Michel Lespinasse <walken@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Anton Blanchard <anton@samba.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: paul.gortmaker@windriver.com Link: http://lkml.kernel.org/r/1359716356-23865-1-git-send-email-yuanhan.liu@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* lib: reduce the use of module.h wherever possiblePaul Gortmaker2012-03-071-1/+1
| | | | | | | | | | For files only using THIS_MODULE and/or EXPORT_SYMBOL, map them onto including export.h -- or if the file isn't even using those, then just delete the include. Fix up any implicit include dependencies that were being masked by module.h along the way. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
* locking, rwsem: Annotate inner lock as rawThomas Gleixner2011-09-131-19/+19
| | | | | | | | | | | | 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>
* rwsem generic spinlock: use IRQ save/restore spinlocksKevin Hilman2010-04-071-6/+8
| | | | | | | | | | | | | rwsems can be used with IRQs disabled, particularily in early boot before IRQs are enabled. Currently the spin_unlock_irq() usage in the slow-patch will unconditionally enable interrupts and cause problems since interrupts are not yet initialized or enabled. This patch uses save/restore versions of IRQ spinlocks in the slowpath to ensure interrupts are not unintentionally disabled. Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* rwsem: fix rwsem_is_locked() bugsAmerigo Wang2009-12-151-0/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* rwsem-spinlock: remove useless function exportsAmerigo Wang2009-12-151-9/+1
| | | | | | | | | | | | These functions need not to be exported, since no drivers should use them. __init_rwsem() is an exception, because init_rwsem(), which is a macro, is used. Signed-off-by: WANG Cong <amwang@redhat.com> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* lib: remove fastcall from lib/*Harvey Harrison2008-02-081-8/+8
| | | | | | | [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>
* Lockdep: add lockdep_set_class_and_subclass() and lockdep_set_subclass()Peter Zijlstra2006-10-111-1/+1
| | | | | | | | | | | | | This annotation makes it possible to assign a subclass on lock init. This annotation is meant to reduce the _nested() annotations by assigning a default subclass. One could do without this annotation and rely on lockdep_set_class() exclusively, but that would require a manual stack of struct lock_class_key objects. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
* [PATCH] lockdep: prove rwsem locking correctnessIngo Molnar2006-07-031-3/+17
| | | | | | | | | 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>
* [PATCH] lockdep: clean up rwsemsIngo Molnar2006-07-031-44/+2
| | | | | | | | Clean up rwsems. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] use smp_mb/wmb/rmb where possibleakpm@osdl.org2005-05-011-3/+3
| | | | | | | | | Replace a number of memory barriers with smp_ variants. This means we won't take the unnecessary hit on UP machines. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* Linux-2.6.12-rc2Linus Torvalds2005-04-161-0/+344
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!
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