Re: [PATCH v9 2/5] qrwlock x86: Enable x86 to use queue read/writelock

From: Peter Zijlstra
Date: Mon Jan 20 2014 - 11:09:02 EST

On Tue, Jan 14, 2014 at 11:44:04PM -0500, Waiman Long wrote:
> This patch makes the necessary changes at the x86 architecture specific
> layer to enable the presence of the CONFIG_QUEUE_RWLOCK kernel option
> to replace the read/write lock by the queue read/write lock.
> It also enables the CONFIG_QUEUE_RWLOCK option by default for x86 which
> will force the use of queue read/write lock. That will greatly improve
> the fairness of read/write lock and eliminate live-lock situation
> where one task may not get the lock for an indefinite period of time.
> Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
> Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/include/asm/spinlock.h | 2 ++
> arch/x86/include/asm/spinlock_types.h | 4 ++++
> 3 files changed, 7 insertions(+), 0 deletions(-)

This patch doesn't have nearly enough -, you should rip out all traces
of the old rwlock. There's no point in having it configurable, either
qrwlock is good or not.
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