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Re: [PATCH] xen/locks: add dynamic lock recursion checks
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 8 Sep 2022 15:08:27 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 08 Sep 2022 13:08:41 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.09.2022 09:46, Juergen Gross wrote:
> Add checking of lock recursion to the hypervisor. This is done by using
> a percpu data array for storing the address of each taken lock. Any
> attempt to take a lock twice (with the exception of recursive
> spinlocks) will result in a crash. This is especially meant for
> detecting attempts to take a rwlock multiple times as a reader, which
> will only result in a deadlock in case of another cpu trying to get the
> lock as a writer in between.
>
> The additional checks are not performance neutral, so they are enabled
> only in debug builds per default, as the checks are active only with
> CONFIG_DEBUG_LOCKS enabled. The size of the percpu data array can be
> selected via a boot parameter.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> Further possible enhancements:
> - record address or file/line of locker, too
> - add sanity check when exiting hypervisor or going to idle that all locks
> have been released
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
But left in the queue for 4.18, ftaod.
Jan
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