Re: [UPDATE PATCH][Bug 5132] fix sys_poll() large timeout handling

[Andrew Morton]

Nishanth Aravamudan <nacc@xxxxxxxxxx> wrote:
>
> +	/*
>  +	 * We compare HZ with 1000 to work out which side of the
>  +	 * expression needs conversion.  Because we want to avoid
>  +	 * converting any value to a numerically higher value, which
>  +	 * could overflow.
>  +	 */
>  +#if HZ > 1000
>  +	overflow = timeout_msecs >= jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT);
>  +#else
>  +	overflow = msecs_to_jiffies(timeout_msecs) >= MAX_SCHEDULE_TIMEOUT;
>  +#endif
>  +
>  +	/*
>  +	 * If we would overflow in the conversion or a negative timeout
>  +	 * is requested, sleep indefinitely.
>  +	 */
>  +	if (overflow || timeout_msecs < 0)
>  +		timeout_jiffies = MAX_SCHEDULE_TIMEOUT;

Do we need to test (timeout_msecs < 0) here?  If we make timeout_msecs
unsigned long then I think `overflow' will always be correct.

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