netdev - Re: [PATCH v2] net: fec: Use unlocked timecounter reads for saving state

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Message-ID: <Yw4ClKHWACSP2EQ1@lunn.ch>
Date:   Tue, 30 Aug 2022 14:29:08 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Csókás Bence <csokas.bence@...lan.hu>
Cc:     netdev@...r.kernel.org, Richard Cochran <richardcochran@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, qiangqing.zhang@....com,
        kernel@...gutronix.de, Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: [PATCH v2] net: fec: Use unlocked timecounter reads for saving
 state

> -	fec_ptp_gettime(&fep->ptp_caps, &fep->ptp_saved_state.ts_phc);
> +	if (preempt_count_equals(0)) {

~/linux/drivers$ grep -r preempt_count_equals *
~/linux/drivers$ 

No other driver plays games like this.

Why not unconditionally take the lock?

    Andrew