Return-path: Received: from mail.deathmatch.net ([72.66.92.28]:3622 "EHLO mail.deathmatch.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751067AbZETDif (ORCPT ); Tue, 19 May 2009 23:38:35 -0400 Date: Tue, 19 May 2009 23:37:31 -0400 From: Bob Copeland To: Steven Rostedt , linville@tuxdriver.com Cc: Nick Kossifidis , LKML , jirislaby@gmail.com, lrodriguez@atheros.com, linux-wireless@vger.kernel.org, ath5k-devel@lists.ath5k.org, Andrew Morton Subject: [PATCH] ath5k: avoid and warn on potential infinite loop Message-ID: <20090520033731.GA16640@hash.localnet> References: <40f31dec0905181734t6a3db7f4peb2d57c3aebe075b@mail.gmail.com> <40f31dec0905182332v49aff368oe485efaa56fbc11a@mail.gmail.com> <20090519114240.GA13934@hash.localnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-wireless-owner@vger.kernel.org List-ID: If we are trying to interpolate a curve with slope == 0, the return value will always be the y-coordinate. In this code we are looping until we reach a minimum y-coordinate on a line, which in the 0-slope case can never happen, thus the loop never terminates. The PCDAC steps come from the EEPROM and should never be equal, but we should gracefully handle that case, so warn and bail out. Reported-by: Steven Rostedt Signed-off-by: Bob Copeland --- This ok? (based on top of the wireless-testing tree -- the patch that's already there can go for 2.6.30. This is in addition to that patch, this handles the other, unlikely, corner case.) Having looked at the code, I don't see why we need to loop at all, couldn't we just invert the slope and solve directly for y=0? Certainly recomputing the slope in a loop could be optimized. Anyway, that's another patch for another day. drivers/net/wireless/ath/ath5k/phy.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/drivers/net/wireless/ath/ath5k/phy.c b/drivers/net/wireless/ath/ath5k/phy.c index d0d1c35..a876ca8 100644 --- a/drivers/net/wireless/ath/ath5k/phy.c +++ b/drivers/net/wireless/ath/ath5k/phy.c @@ -1897,6 +1897,9 @@ ath5k_get_linear_pcdac_min(const u8 *stepL, const u8 *stepR, s16 min_pwrL, min_pwrR; s16 pwr_i; + if (WARN_ON(stepL[0] == stepL[1] || stepR[0] == stepR[1])) + return 0; + if (pwrL[0] == pwrL[1]) min_pwrL = pwrL[0]; else { -- 1.6.0.6 -- Bob Copeland %% www.bobcopeland.com