From: Patrick McHardy <kaber@trash•net>
To: Corey Hickey <bugfood-ml@fatooh•org>
Cc: netdev@vger•kernel.org
Subject: Re: [PATCH 09/10] Change perturb_period to unsigned.
Date: Mon, 01 Oct 2007 15:45:38 +0200 [thread overview]
Message-ID: <4700FA02.8090800@trash.net> (raw)
In-Reply-To: <11910199784097-git-send-email-bugfood-ml@fatooh.org>
Corey Hickey wrote:
> perturb_period is currently a signed integer, but I can't see any good
> reason why this is so--a negative perturbation period will add a timer
> that expires in the past, causing constant perturbation, which makes
> hashing useless.
>
> if (q->perturb_period) {
> q->perturb_timer.expires = jiffies + q->perturb_period;
> add_timer(&q->perturb_timer);
> }
>
> Strictly speaking, this will break binary compatibility with older
> versions of tc, but that ought not to be a problem because (a) there's
> no valid use for a negative perturb_period, and (b) negative values
> will be seen as high values (> INT_MAX), which don't work anyway.
>
> If perturb_period is too large, (perturb_period * HZ) will overflow the
> size of an unsigned int and wrap around. So, check for thet and reject
> values that are too high.
Sounds reasonable.
> --- a/net/sched/sch_sfq.c
> +++ b/net/sched/sch_sfq.c
> @@ -74,6 +74,9 @@
> typedef unsigned int sfq_index;
> #define SFQ_MAX_DEPTH (UINT_MAX / 2 - 1)
>
> +/* We don't want perturb_period * HZ to overflow an unsigned int. */
> +#define SFQ_MAX_PERTURB (UINT_MAX / HZ)
jiffies are unsigned long.
next prev parent reply other threads:[~2007-10-01 13:46 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-28 22:52 SFQ: backport some features from ESFQ (try 4) Corey Hickey
2007-09-28 22:52 ` [PATCH 01/10] Preparatory refactoring part 1 Corey Hickey
2007-10-01 13:25 ` Patrick McHardy
2007-10-01 20:46 ` Corey Hickey
2007-10-02 3:17 ` Patrick McHardy
2007-09-28 22:52 ` [PATCH 02/10] Preparatory refactoring part 2 Corey Hickey
2007-10-01 13:33 ` Patrick McHardy
2007-10-01 20:46 ` Corey Hickey
2007-10-02 3:19 ` Patrick McHardy
2007-09-28 22:52 ` [PATCH 03/10] Move two functions Corey Hickey
2007-10-01 13:27 ` Patrick McHardy
2007-10-01 20:46 ` Corey Hickey
2007-09-28 22:52 ` [PATCH 04/10] Make "depth" (number of queues) user-configurable: Corey Hickey
2007-09-28 22:52 ` [PATCH 05/10] Add divisor Corey Hickey
2007-10-01 13:38 ` Patrick McHardy
2007-10-01 20:47 ` Corey Hickey
2007-09-28 22:52 ` [PATCH 06/10] Make qdisc changeable Corey Hickey
2007-10-01 13:43 ` Patrick McHardy
2007-10-01 20:47 ` Corey Hickey
2007-09-28 22:52 ` [PATCH 07/10] Remove comments about hardcoded values Corey Hickey
2007-09-28 22:52 ` [PATCH 08/10] Multiply perturb_period by HZ when used rather than when assigned Corey Hickey
2007-09-28 22:52 ` [PATCH 09/10] Change perturb_period to unsigned Corey Hickey
2007-10-01 13:45 ` Patrick McHardy [this message]
2007-10-01 20:47 ` Corey Hickey
2007-09-28 22:52 ` [PATCH 10/10] Use nested compat attributes to pass parameters Corey Hickey
2007-10-01 13:54 ` Patrick McHardy
2007-10-01 20:47 ` Corey Hickey
2007-10-02 3:21 ` Patrick McHardy
2007-09-28 22:54 ` sfq Corey Hickey
2007-09-28 22:57 ` sfq (iproute2 patches) Corey Hickey
2007-09-28 22:54 ` [PATCH 1/3] SFQ: Support changing depth and divisor Corey Hickey
2007-09-28 22:54 ` [PATCH 2/3] Change perturb_period to unsigned Corey Hickey
2007-09-28 22:54 ` [PATCH 3/3] Use nested compat attributes for passing parameters to the kernel Corey Hickey
2007-09-29 15:38 ` SFQ: backport some features from ESFQ (try 4) Patrick McHardy
2007-09-29 17:36 ` Corey Hickey
-- strict thread matches above, loose matches on Subject: below --
2007-08-25 22:26 [PATCH 00/10] SFQ: backport some features from ESFQ (try 3) Corey Hickey
2007-08-25 22:27 ` [PATCH 09/10] Change perturb_period to unsigned Corey Hickey
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