Re: [PATCH v3] doc:lock: remove reference to clever use of read-write lock
From: Will Deacon
Date: Thu Sep 12 2019 - 09:32:34 EST
On Sun, Sep 08, 2019 at 08:29:01AM +0200, Federico Vaga wrote:
> Remove the clever example about read-write lock because this type of
> lock is not reccomended anymore (according to the very same document).
reccomended => recommended
> So there is no reason to teach cleaver things that people should not do.
cleaver => clever
> Signed-off-by: Federico Vaga <federico.vaga@xxxxxxxxxx>
> Documentation/locking/spinlocks.rst | 12 ------------
> 1 file changed, 12 deletions(-)
> diff --git a/Documentation/locking/spinlocks.rst b/Documentation/locking/spinlocks.rst
> index e93ec6645238..66e3792f8a36 100644
> --- a/Documentation/locking/spinlocks.rst
> +++ b/Documentation/locking/spinlocks.rst
> @@ -139,18 +139,6 @@ on other CPU's, because an interrupt on another CPU doesn't interrupt the
> CPU that holds the lock, so the lock-holder can continue and eventually
> releases the lock).
> -Note that you can be clever with read-write locks and interrupts. For
> -example, if you know that the interrupt only ever gets a read-lock, then
> -you can use a non-irq version of read locks everywhere - because they
> -don't block on each other (and thus there is no dead-lock wrt interrupts.
> -But when you do the write-lock, you have to use the irq-safe version.
> -For an example of being clever with rw-locks, see the "waitqueue_lock"
> -handling in kernel/sched/core.c - nothing ever _changes_ a wait-queue from
> -within an interrupt, they only read the queue in order to know whom to
> -wake up. So read-locks are safe (which is good: they are very common
> -indeed), while write-locks need to protect themselves against interrupts.
With the typos fixed in the commit message:
Acked-by: Will Deacon <will@xxxxxxxxxx>