From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: [PATCH] IRQ: don't suspend nested_thread irqs over system suspend. Date: Sat, 31 Jan 2015 14:37:47 +1100 Message-ID: <20150131143747.7b9a4f10@notabene.brown> References: <20150131092545.33ed35b8@notabene.brown> <1465455.9L1ju05BhM@vostro.rjw.lan> <7535701.LlWsyNLDEC@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/VyU9OGfJIcfK+NL+GSEgEso"; protocol="application/pgp-signature" Return-path: Received: from cantor2.suse.de ([195.135.220.15]:46737 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752179AbbAaDiA (ORCPT ); Fri, 30 Jan 2015 22:38:00 -0500 In-Reply-To: <7535701.LlWsyNLDEC@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, GTA04 owners , linux-pm@vger.kernel.org, Kalle Jokiniemi --Sig_/VyU9OGfJIcfK+NL+GSEgEso Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Sat, 31 Jan 2015 00:51:17 +0100 "Rafael J. Wysocki" wrote: > On Saturday, January 31, 2015 12:06:37 AM Rafael J. Wysocki wrote: > > On Saturday, January 31, 2015 09:25:45 AM NeilBrown wrote: > > >=20 > > > Nested IRQs can only fire when the parent irq fires. > > > So when the parent is suspended, there is no need to suspend > > > the child irq. > > >=20 > > > Suspending nested irqs can cause a problem is they are suspended or > > > resumed in the wrong order. > > > If an interrupt fires while the parent is active but the child is > > > suspended, then the interrupt will not be acknowledged properly > > > and so an interrupt storm can result. > > > This is particularly likely if the parent is resumed before > > > the child, and the interrupt was raised during suspend. > > >=20 > > > Ensuring correct ordering would be possible, but it is simpler > > > to just never suspend nested interrupts. This patch does that. > >=20 > > Clever. :-) > >=20 > > This is fine by me. Thomas, what do you think? >=20 > It looks like I've overlooked a potential problem, though. >=20 > Can a nested interrupt be a wakeup one? We won't set IRQD_WAKEUP_ARMED f= or it > then and may not handle wakeup correctly. >=20 I only have a fairly narrow understanding of this stuff, but if you have nested interrupts, you would surely need the parent to be registered as a wakeup interrupt, else the device wouldn't wake and the nested interrupt would be ineffective until something else woke the device. Very few files mention both '.irq_set_wake' and 'irq_set_nested'. twl6040-irq.c has code to set irq_wake_enable on the parent if any nested irqs have had irq_set_wake calls. tps6586x.c has something similar, but much simpler. arizona-irq.c and rc5t583-irq.c do the same as tps6586x.c So I think that any nested interrupts which might want to be wakeup interrupts already deal with the issue, and I don't introduce a new problem here. Thanks, NeilBrown > > > This patch allows the IRQF_EARLY_RESUME to be removed from > > > twl4030_sih_setup(). That flag attempts to fix the same problem > > > is a very different way, but causes > > >=20 > > > [ 56.095825] WARNING: CPU: 0 PID: 3 at ../kernel/irq/manage.c:661 i= rq_nested_primary_handler+0x18/0x28() > > > [ 56.095825] Primary handler called for nested irq 348 > > >=20 > > > warnings on resume. > > >=20 > > > Signed-off-by: NeilBrown > > >=20 > > > diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c > > > index 3ca532592704..40cbcfb7fc43 100644 > > > --- a/kernel/irq/pm.c > > > +++ b/kernel/irq/pm.c > > > @@ -118,6 +118,8 @@ void suspend_device_irqs(void) > > > unsigned long flags; > > > bool sync; > > > =20 > > > + if (irq_settings_is_nested_thread(desc)) > > > + continue; > > > raw_spin_lock_irqsave(&desc->lock, flags); > > > sync =3D suspend_device_irq(desc, irq); > > > raw_spin_unlock_irqrestore(&desc->lock, flags); > > > @@ -158,6 +160,8 @@ static void resume_irqs(bool want_early) > > > =20 > > > if (!is_early && want_early) > > > continue; > > > + if (irq_settings_is_nested_thread(desc)) > > > + continue; > > > =20 > > > raw_spin_lock_irqsave(&desc->lock, flags); > > > resume_irq(desc, irq); > >=20 > >=20 >=20 --Sig_/VyU9OGfJIcfK+NL+GSEgEso Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIVAwUBVMxOCznsnt1WYoG5AQLTKxAAmoE3/G5/qQYM5aOcYeU2bp0/ucTE5Ev6 ovGlO7p5INOA/8lthRvLFOHgWrYSBL0Gn9+mujdWPCY8066/j7AL+nAxxr8SpndD f6jusd2GWB3fEIGO2AS/4ogwyC8VXjJ3Nb07QSiT5dULz62zQtAGV8NMZx+q3aWu kRa5eI2I83j200Udo3Ya0Qi0Atve2KhLmH5Wnsmo2T80esn1z2MsfpjODDjY2o/v uLttOqnfDlcQ/54V+NFmssMpPYc2eco5LWeOd+EsOmOwS0T+M4FF2XukpcUIftSo hc9JSgJ3yE/U+WKfjh1JC193HipLdKMHKDAp+k4i9I/vnQf3V1hGkwWwFUeCyPBA 42U7iSXCXNd6rP/ejkIsxXMTRBfFhqvevUaRP/Zb2MBbpqfdQtB8c/40O4l1Bq0Z 6Xrfondf8KE1ywm+4MzxuA64ZB5zwoZDRmuc1dkB/vsUhmaqXa6cwtGgEJC4tkXb YzWU4Mi+4HInejNiDsms7r8PspVekQSVlbp28Oi48/39rrbn+NZRbzynBNxoLsvq nNNjNjxYEZRjvDpCqdzkKPZy/FnnOtVbeVdRzIErYpYL2yHYhCuUY1gKe41XSNUe J79c2uuBlrU4UewWbBC98h4vNP1eiAM65Atb6hRif4tjkifvyMZNIlQc6Ireajrr 0YbGIy1DqkI= =ZxEi -----END PGP SIGNATURE----- --Sig_/VyU9OGfJIcfK+NL+GSEgEso--