Eric Lee / smarc-fsl-linux-kernel

07 May, 2013

2 commits

  • 8cf5322ce   rwsem: simplify __rwsem_do_wake ... Browse Code »

    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
    Reviewed-by: Peter Hurley
    Acked-by: Davidlohr Bueso
    Signed-off-by: Linus Torvalds

    Michel Lespinasse
     
  • e2d57f782   rwsem: make the waiter type an enumeration rather than a bitmask ... Browse Code »

    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
    Reviewed-by: Rik van Riel
    Reviewed-by: Peter Hurley
    Acked-by: Davidlohr Bueso
    Signed-off-by: Linus Torvalds

    Michel Lespinasse
     

19 Feb, 2013

1 commit

  • 41ef8f826   rwsem-spinlock: Implement writer lock-stealing for better scalability ... Browse Code »

    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
    Suggested-by: Ingo Molnar
    Signed-off-by: Yuanhan Liu
    Cc: Alex Shi
    Cc: David Howells
    Cc: Michel Lespinasse
    Cc: Linus Torvalds
    Cc: Andrew Morton
    Cc: Peter Zijlstra
    Cc: Anton Blanchard
    Cc: Arjan van de Ven
    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

    Yuanhan Liu
     

08 Mar, 2012

1 commit

13 Sep, 2011

1 commit

  • ddb6c9b58   locking, rwsem: Annotate inner lock as raw ... Browse Code »

    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

    Thomas Gleixner
     

08 Apr, 2010

1 commit

  • 3eac4abaa   rwsem generic spinlock: use IRQ save/restore spinlocks ... Browse Code »

    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
    Signed-off-by: Linus Torvalds

    Kevin Hilman
     

16 Dec, 2009

2 commits

  • 29671f22a   rwsem: fix rwsem_is_locked() bugs ... Browse Code »

    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

    Amerigo Wang
     
  • 118d52da1   rwsem-spinlock: remove useless function exports ... Browse Code »

    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
    Cc: David Howells
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Amerigo Wang
     

09 Feb, 2008

1 commit

11 Oct, 2006

1 commit

04 Jul, 2006

2 commits

01 May, 2005

1 commit

17 Apr, 2005

1 commit

  • 1da177e4c   Linux-2.6.12-rc2 ... Browse Code »

    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!

    Linus Torvalds