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Re: [PATCH] xen/spinlock: move debug helpers inside the locked regions

On 29/07/2020 15:57, Julien Grall wrote:
Hi Roger,

On 29/07/2020 14:50, Roger Pau Monné wrote:
On Wed, Jul 29, 2020 at 02:37:44PM +0100, Julien Grall wrote:
Hi Roger,

On 29/07/2020 12:13, Roger Pau Monne wrote:
Debug helpers such as lock profiling or the invariant pCPU assertions
must strictly be performed inside the exclusive locked region, or else
races might happen.

Note the issue was not strictly introduced by the pointed commit in
the Fixes tag, since lock stats where already incremented before the
barrier, but that commit made it more apparent as manipulating the cpu
field could happen outside of the locked regions and thus trigger the

 From the wording, it is not entirely clear which BUG_ON() you are referring
to. I am guessing, it is the one in rel_lock(). Am I correct?

Yes, that's right. Expanding to:

"...  and thus trigger the BUG_ON in rel_lock()." would be better.

Looks good to me. With that:

Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

I am happy to do the update on commit if there is no more comments.


Thank you!


Julien Grall



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