From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5875534FF50 for ; Fri, 20 Mar 2026 16:58:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774025925; cv=none; b=pLAS3b5DD3aYsTLUHYEFXtu4pkh0AVuNhJ7WAX6JQ7r/0JdU5eTlbGnSlPNiAE4D0kV0yceoQ23+2Cuf33QLbmZxLzyMeoXznfW2Ihf6hrery1qmeLp3hohVlvao1lDpaLQe4LlJGm08WCVMtcH5DP5O0WvpbqqAuXC8VT9zQlY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774025925; c=relaxed/simple; bh=9cTvHpx+iUaz4u0VYLluXXZpeFM/77t2ZMUS/xtb23M=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=TZgExUIiGzOmUjxUtDOx5s+Uf0pTp2xMdNoZHjvYARqxtcb31vI+GoY3tKEEcVUEEgypObIw5MnAqELkMThdIUNzbIi8iHaz986xlZwMxCK/MHHQwF7aCAWR/daRY50y/6Q9bB2lEr6JgeuxR7QboTVzH18jjY9Z4XXh/T5mfvg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=econGwhJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="econGwhJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B38AC19425; Fri, 20 Mar 2026 16:58:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774025925; bh=9cTvHpx+iUaz4u0VYLluXXZpeFM/77t2ZMUS/xtb23M=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=econGwhJwUL2RCt3lzQdFMcfEdoI9wB+Gnw0no9wMX+tMZ60172Y+4zMvi0oQpGPH 9yncrx0fNU/1WG3mHIRVfMj4Ecriil6u0WOmMvt72VhxjcpGGVjlBG5M/6IqdF9FuE w8/cYUQ9wtyuRh+0IV9ycpFC0iNKiJvW8zUZnIWVIG6G1jqBwObVja47is1vIKxVTB 3eDV2t9Q/BeuRT2jYSNY0Hcsf0kGJgugNsHcIF9e4tvXFPOkYGWk7Qr3W+5MJVcipQ XEpubfNtFBzELqaVj/HfpwjqrpA/J8on7j8CoxHs02o8/u+E2FVJScHwMINCwlMONi 9PK01qLQHfQYA== From: Thomas Gleixner To: Connor Williamson , jstultz@google.com, sboyd@kernel.org Cc: linux-kernel@vger.kernel.org, nh-open-source@amazon.com, paulmck@kernel.org, connordw@amazon.com Subject: Re: [PATCH timers/core v1] clocksource: Align clocksource watchdog constraints with Kconfig value In-Reply-To: <20260313142939.3023-1-connordw@amazon.com> References: <20260313142939.3023-1-connordw@amazon.com> Date: Fri, 20 Mar 2026 17:58:41 +0100 Message-ID: <87wlz6igji.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Fri, Mar 13 2026 at 14:29, Connor Williamson wrote: > A previous patch intended to update both MAX_SKEW_USEC and > CLOCKSOURCE_WATCHDOG_MAX_SKEW_US to 125 microseconds, resulting in a > total tolerable skew per second of 500 microseconds as this value is > doubled prior to being associated with the uncertainty_margin of a > clocksource, and the uncertainty_margin values of two clocksources being > compared are then summed before comparison to the skew. > > However, the default value of MAX_SKEW_USEC in the absence of the > Kconfig option was defined as (125 * WATCHDOG_INTERVAL / HZ), which is > (125 * (HZ >> 1)) / HZ, effectively ~ 125/2 microseconds, while > CLOCKSOURCE_WATCHDOG_MAX_SKEW_US was set to 125 microseconds as > intended. Q: How does that matter? A: Not at all. CLOCKSOURCE_WATCHDOG_MAX_SKEW_US is always defined when CLOCKSOURCE_WATCHDOG=y. IOW, the #else path is simply dead code. > Therefore, align MAX_SKEW_USEC with CLOCKSOURCE_WATCHDOG_MAX_SKEW_US, > setting it to the intended default value of 125 microseconds. > > 'Fixes: c37e85c135ce ("clocksource: Loosen clocksource watchdog > constraints")' Bogus format for the Fixes tag. Please read and follow Documentation. It's there for a reason. But that doesn't matter much because this patch fixes clearly nothing. The only valid "fix" is to delete the dead code and not to polish it, but that's pretty moot as it is harmless and already scheduled for removal in 7.1 due to: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=timers/core Thanks, tglx