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Re: [PATCH v3 2/3] xen/locking: harmonize spinlocks and rwlocks regarding preemption

To: Juergen Gross <jgross@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
From: Julien Grall <julien@xxxxxxx>
Date: Wed, 4 Nov 2020 09:38:15 +0000
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
Delivery-date: Wed, 04 Nov 2020 09:38:24 +0000
List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

Hi Juergen,

On 04/11/2020 08:15, Juergen Gross wrote:

Spinlocks and rwlocks behave differently in the try variants regarding
preemption: rwlocks are switching preemption off before testing the
lock, while spinlocks do so only after the first check.

Modify _spin_trylock() to disable preemption before testing the lock
to be held in order to be preemption-ready.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>


Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall

References:
- [PATCH v3 0/3] xen/locking: fix and enhance lock debugging
  - From: Juergen Gross
- [PATCH v3 2/3] xen/locking: harmonize spinlocks and rwlocks regarding preemption
  - From: Juergen Gross

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