From: Vinicius Costa Gomes <vinicius.gomes@intel.com>
To: "Kolacinski, Karol" <karol.kolacinski@intel.com>,
"Nguyen, Anthony L" <anthony.l.nguyen@intel.com>,
"intel-wired-lan@lists.osuosl.org"
<intel-wired-lan@lists.osuosl.org>
Subject: Re: [Intel-wired-lan] [PATCH net-next 2/2] ice: Remove gettime HW semaphore
Date: Wed, 05 Oct 2022 14:10:33 -0700 [thread overview]
Message-ID: <87bkqqou2e.fsf@intel.com> (raw)
In-Reply-To: <MW4PR11MB5800C7EFFCA3CFE32A351EFB865D9@MW4PR11MB5800.namprd11.prod.outlook.com>
"Kolacinski, Karol" <karol.kolacinski@intel.com> writes:
> Hi Vinicius,
>
>> I think the problem is less about concurrent writes/reads than
>> concurrent reads: the fact that the registers are latched when the
>> "lower" register is read, makes me worried that there's a (very narrow)
>> window during rollover in which the "losing" read (of multiple threads
>> doing reads) can return a wrong value.
>
> The issue in this case is, it's either risk of reading slightly wrong
> value or having multiple timeouts and errors.
> We experienced a lot of simultaneous reads on multiple PFs (especially
> on E822 HW with 8 ports) and even with increased timeout to acquire
> the HW semaphore, it still failed.
I am wondering if using a hw semaphore is making the problem worse than
it needs to be. Why a kernel spinlock can't be used?
Cheers,
--
Vinicius
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next prev parent reply other threads:[~2022-10-05 21:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-03 9:55 [Intel-wired-lan] [PATCH net-next 1/2] ice: Check for PTP HW lock more frequently Karol Kolacinski
2022-10-03 9:55 ` [Intel-wired-lan] [PATCH net-next 2/2] ice: Remove gettime HW semaphore Karol Kolacinski
2022-10-03 18:03 ` Tony Nguyen
2022-10-05 11:55 ` Kolacinski, Karol
2022-10-05 21:10 ` Vinicius Costa Gomes [this message]
2022-10-17 22:52 ` Jacob Keller
2022-10-18 0:50 ` Vinicius Costa Gomes
2022-11-11 4:38 ` G, GurucharanX
2022-11-11 4:39 ` [Intel-wired-lan] [PATCH net-next 1/2] ice: Check for PTP HW lock more frequently G, GurucharanX
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