linux-kernel - Re: [PATCH] eeprom: at24: Fix unexpected timeout under high load

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Message-ID: <CAHp75Veo__Zu_Uk5-CN5q_yEUHs0fDsKZu9van89JBX2Prs7-w@mail.gmail.com>
Date:   Sat, 4 Aug 2018 23:51:37 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Mark Jonas <mark.jonas@...bosch.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Wang Xin <xin.wang7@...bosch.com>
Subject: Re: [PATCH] eeprom: at24: Fix unexpected timeout under high load

On Sat, Aug 4, 2018 at 8:43 PM, Mark Jonas <mark.jonas@...bosch.com> wrote:


> -#define at24_loop_until_timeout(tout, op_time)                         \
> -       for (tout = jiffies + msecs_to_jiffies(at24_write_timeout),     \
> -            op_time = 0;                                               \
> -            op_time ? time_before(op_time, tout) : true;               \
> -            usleep_range(1000, 1500), op_time = jiffies)

This one understandble and represents one operation.

> +#define at24_loop_until_timeout_begin(tout, op_time)           \
> +       tout = jiffies + msecs_to_jiffies(at24_write_timeout);  \
> +       while (true) {                                          \
> +               op_time = jiffies;
> +
> +#define at24_loop_until_timeout_end(tout, op_time)             \
> +               if (time_before(tout, op_time))                 \
> +                       break;                                  \
> +               usleep_range(1000, 1500);                       \
> +       }

Besides `while (true)`, which is a red flag for timeout loops,
these are done in an hack way. Just open code them in both cases, or
rewrite original one to keel it's semantics.

-- 
With Best Regards,
Andy Shevchenko