Re: [PATCH v2] crypto: run qcrypto_pbkdf2_count_iters in a new thread

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Sep 04, 2024 at 08:52:30PM -0300, Tiago Pasqualini wrote:
> CPU time accounting in the kernel has been demonstrated to have a
> sawtooth pattern[1][2]. This can cause the getrusage system call to
> not be as accurate as we are expecting, which can cause this calculation
> to stall.
> 
> The kernel discussions shows that this inaccuracy happens when CPU time
> gets big enough, so this patch changes qcrypto_pbkdf2_count_iters to run
> in a fresh thread to avoid this inaccuracy. It also adds a sanity check
> to fail the process if CPU time is not accounted.
> 
> [1] https://lore.kernel.org/lkml/159231011694.16989.16351419333851309713.tip-bot2@tip-bot2/
> [2] https://lore.kernel.org/lkml/20221226031010.4079885-1-maxing.lan@bytedance.com/t/#m1c7f2fdc0ea742776a70fd1aa2a2e414c437f534
> 
> Resolves: #2398
> Signed-off-by: Tiago Pasqualini <tiago.pasqualini@canonical.com>
> ---
>  crypto/pbkdf.c | 53 +++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 46 insertions(+), 7 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

and queued.

With regards,
Daniel
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