From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752876AbbJNK11 (ORCPT ); Wed, 14 Oct 2015 06:27:27 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:58253 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751501AbbJNK1Z (ORCPT ); Wed, 14 Oct 2015 06:27:25 -0400 Date: Wed, 14 Oct 2015 11:27:06 +0100 From: Mark Brown To: Peter Zijlstra Cc: Arnd Bergmann , Ingo Molnar , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Liam Girdwood , akpm@linux-foundation.org, Sascha Hauer Message-ID: <20151014102706.GR14956@sirena.org.uk> References: <11282238.AHmyWliPRj@wuerfel> <20151013203812.GM17308@twins.programming.kicks-ass.net> <11817958.z9KtmeKzV7@wuerfel> <20151014082050.GQ17308@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="1IOPqZ3f1xe/JZlz" Content-Disposition: inline In-Reply-To: <20151014082050.GQ17308@twins.programming.kicks-ass.net> X-Cookie: Do you like "TENDER VITTLES"? User-Agent: Mutt/1.5.24 (2015-08-30) X-SA-Exim-Connect-IP: 94.175.94.161 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [PATCH] mutex: make mutex_lock_nested an inline function X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --1IOPqZ3f1xe/JZlz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Oct 14, 2015 at 10:20:50AM +0200, Peter Zijlstra wrote: > Uuh, I just looked at next and saw this regulator_lock_supply() > function. How is that limited? subclass must be <8 otherwise bad things > happen. Can we please get some more discoverable documentation of the arbitrary limits in the lockdep code? I seem to keep seeing code that bumps into surprising limits like this and I'm not sure how I'm supposed to know about them except through finding out after the fact or trawling the code every time someone touches locking. I would be very surprised to see a system that pushes over 8 locks, while there's nothing actually preventing it system design considerations mean that even four cascaded supplies are pretty unlikely so we should be fine. Every time you add a new level of regulation you're both increasing the load on regulators up the chain (which means they need to be bigger and more expensive) and except in the case of a DCDC supplying an LDO (which only works to one level) you're going to be decreasing the efficiency of the system. If we get to that point we can worry about what to do. --1IOPqZ3f1xe/JZlz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJWHi35AAoJECTWi3JdVIfQ8ksH/AnBkf9rK4SdXX/DTphQ6eqD yUKOuzQ+fxJb+k+hhRI5ltIDSzB/+i/We2IhQuB2wP+6mOcjFvmWLZenUA3d4JF8 onKHOicRCjJc6eQyevXNQKjOYW77mARzLFpo9Ht8AzX/Pxmpl9ML44g/hPB3w4fH hA2rzSg7/KsGsJadJKkIc/URgvdKm90uWmkd3RBlDSKVQW7q8YIXGwiKhJVYKVs4 qZBCrZT11qBW8HcE6At9/bMVGhxpLXynysjYIchSghwYAv27+2N8XFpR/REbniRM xxWZv3TYyDKutMAtLBEr37oH7CkQHUn3C9nBVirfXTjElz3QYrqeKjbvw+qqaJg= =+uHw -----END PGP SIGNATURE----- --1IOPqZ3f1xe/JZlz--