From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 19CD8C4167B for ; Thu, 28 Apr 2022 16:58:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350394AbiD1RBN (ORCPT ); Thu, 28 Apr 2022 13:01:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235928AbiD1RBL (ORCPT ); Thu, 28 Apr 2022 13:01:11 -0400 Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7208BB6D27; Thu, 28 Apr 2022 09:57:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1651164963; bh=DUb16bHT8ZVVcSBzzE8lnieko2RHZpG2zbwsEWdWo2c=; h=X-UI-Sender-Class:Date:Subject:To:Cc:References:From:In-Reply-To; b=TrwFfhoA2P1jqiZSh6qbThQbWQ3kajZ2U+JQrRL/jSZxckwFV1BopRKv6DRaeQSKC DM8QpY2fv9fsoSq055uYb4MCMz8e9HvG+guo2m9xr29cJoYbxYguo2PwZIKFp/JXdB qy9XbYXMKcmj9vbKxczpPpGqEow6LzKi+qj1B+ao= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [192.168.20.60] ([92.116.133.159]) by mail.gmx.net (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MzyuS-1o6TNU3b1S-00x2R3; Thu, 28 Apr 2022 18:56:03 +0200 Message-ID: <6a7c924a-54a9-c5ea-8a9d-3ea92987b436@gmx.de> Date: Thu, 28 Apr 2022 18:55:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH 12/30] parisc: Replace regular spinlock with spin_trylock on panic path Content-Language: en-US To: "Guilherme G. Piccoli" , akpm@linux-foundation.org, bhe@redhat.com, pmladek@suse.com, kexec@lists.infradead.org Cc: linux-kernel@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, coresight@lists.linaro.org, linuxppc-dev@lists.ozlabs.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-edac@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-leds@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-pm@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org, linux-tegra@vger.kernel.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org, netdev@vger.kernel.org, openipmi-developer@lists.sourceforge.net, rcu@vger.kernel.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com, alejandro.j.jimenez@oracle.com, andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de, corbet@lwn.net, d.hatayama@jp.fujitsu.com, dave.hansen@linux.intel.com, dyoung@redhat.com, feng.tang@intel.com, gregkh@linuxfoundation.org, mikelley@microsoft.com, hidehiro.kawai.ez@hitachi.com, jgross@suse.com, john.ogness@linutronix.de, keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org, mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org, rostedt@goodmis.org, senozhatsky@chromium.org, stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com, vkuznets@redhat.com, will@kernel.org, "James E.J. Bottomley" References: <20220427224924.592546-1-gpiccoli@igalia.com> <20220427224924.592546-13-gpiccoli@igalia.com> From: Helge Deller In-Reply-To: <20220427224924.592546-13-gpiccoli@igalia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:5vdTXh07+igNuefls5XBW8Vnc+iEgtAi7WYk6EGDKuqY95FwGMe QwcWZKzUaEoh4UB+55vjZve/tYEaItgGsgQfOqHuHHkvtwYyxsf6YShgZsftQKYSmO6WQ+T ZC1GiQE33MbntUGomNddrKZxDF5sJxGJRqGlvPVNWYXBnGaRnQV/WvjdEKXY9QfAk5iDfpf 2SF7pYcym4psStLDUUMNQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:seIPaj7dpZM=:yycTg0fvdDhrITiv3IZXzI e4yFHTYHbrGUy0XcNvNSnWURkRH0CwdNhQ3CWNfifJgMcKrsF971kE1ZPU9NMQWdlbTy3YHHQ kdbLaclaoLvW+e4KLLE5yocf48/EeAYglXhY84PxWcp1QGdF7y7nXLElZka6kp2R0F8+61JyB loph7JvlvHMoA0h4saDhDgOi28CBTeWf2mZxC+/EkMY8v85s5wN3/znVOlOIi2kLzQZEdEUxg qZqRAEH0zpZWVc5jenddLnwtNUslbH1ysbnT6Jz+8m3SINHv4Rwqo8qzXPYlIEhtABEOB2CCo zGH68oxcPKpqrqbFPSUrvmevYIsFthSN4Qa4ESwcyflnmJb/H2yYOm3idKBPcHZoAc7MXpKFp RR3P6Q1355mAy9N9Htg1IQRALV21oxx1PunXwbHOYiOH77jvrab76cf+pliKkaIi4EdHQpQqw 9mxPXAGH7PZiMiQ7xVCBiONFGbdiXxNWW9WgP8A6pz6E89Sx90IwrTRc9D73bLfwpGwDmjWxi fFfVa4k8dmCqUPhBM1VhxPpxNRnj9QzEWrSQ0xThSfPtnfKEaiZ6CAhESljw6d2UOOHcDSLiC pYk2Il0xe7DktL7r83T2I0B8fYcU06QnK7MXlbmtGkMbQFBGucQc+IB7UEgTcN0uT8ZaS6/FI jkfGMBIY2eSkyrlErzq+vnajUsa0b9zENmsHS55RE7h43gLxmwE2UNFRUH8bWmdFhfJcUWhCo 0TAcvRyne9VEKfs0HrQjTEdgbmSa875UQ1egzran3Xhi4XGH8Atz9id4q//uvXHDPEYGUcpM1 1jCttDZecf4rq/B12RMkoMxP6zY3FZKwK7quDBpUSTid+jJEDxaXtx0XaeJ0Hg0rDMgviRyZ9 HzUcPocKiz/LqCSxQKJ+5LacyVgyzC2Eg/QV5UE+RmBe/a0+mK1ccbKXN/YmWVo5xcoOe11r/ LQC+womcGp8ubOddU8soGYLdecjhj+rpnt5TdzsPY9fawi7HlwarnA+ConVoG4a/SWDHYon/e QtxJhYG5A/NQ3aDfGGrPKFQkR4D9mAqQmSL7oHO9wv65NzEickiapaFqe4ZYqD4oBbohP/rOw OHyJm5CjSYyJJQ= Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/28/22 00:49, Guilherme G. Piccoli wrote: > The panic notifiers' callbacks execute in an atomic context, with > interrupts/preemption disabled, and all CPUs not running the panic > function are off, so it's very dangerous to wait on a regular > spinlock, there's a risk of deadlock. > > This patch refactors the panic notifier of parisc/power driver > to make use of spin_trylock - for that, we've added a second > version of the soft-power function. Also, some comments were > reorganized and trailing white spaces, useless header inclusion > and blank lines were removed. > > Cc: Helge Deller > Cc: "James E.J. Bottomley" > Signed-off-by: Guilherme G. Piccoli You may add: Acked-by: Helge Deller # parisc Helge > --- > arch/parisc/include/asm/pdc.h | 1 + > arch/parisc/kernel/firmware.c | 27 +++++++++++++++++++++++---- > drivers/parisc/power.c | 17 ++++++++++------- > 3 files changed, 34 insertions(+), 11 deletions(-) > > diff --git a/arch/parisc/include/asm/pdc.h b/arch/parisc/include/asm/pdc= .h > index b643092d4b98..7a106008e258 100644 > --- a/arch/parisc/include/asm/pdc.h > +++ b/arch/parisc/include/asm/pdc.h > @@ -83,6 +83,7 @@ int pdc_do_firm_test_reset(unsigned long ftc_bitmap); > int pdc_do_reset(void); > int pdc_soft_power_info(unsigned long *power_reg); > int pdc_soft_power_button(int sw_control); > +int pdc_soft_power_button_panic(int sw_control); > void pdc_io_reset(void); > void pdc_io_reset_devices(void); > int pdc_iodc_getc(void); > diff --git a/arch/parisc/kernel/firmware.c b/arch/parisc/kernel/firmware= .c > index 6a7e315bcc2e..0e2f70b592f4 100644 > --- a/arch/parisc/kernel/firmware.c > +++ b/arch/parisc/kernel/firmware.c > @@ -1232,15 +1232,18 @@ int __init pdc_soft_power_info(unsigned long *po= wer_reg) > } > > /* > - * pdc_soft_power_button - Control the soft power button behaviour > - * @sw_control: 0 for hardware control, 1 for software control > + * pdc_soft_power_button{_panic} - Control the soft power button behavi= our > + * @sw_control: 0 for hardware control, 1 for software control > * > * > * This PDC function places the soft power button under software or > * hardware control. > - * Under software control the OS may control to when to allow to shut > - * down the system. Under hardware control pressing the power button > + * Under software control the OS may control to when to allow to shut > + * down the system. Under hardware control pressing the power button > * powers off the system immediately. > + * > + * The _panic version relies in spin_trylock to prevent deadlock > + * on panic path. > */ > int pdc_soft_power_button(int sw_control) > { > @@ -1254,6 +1257,22 @@ int pdc_soft_power_button(int sw_control) > return retval; > } > > +int pdc_soft_power_button_panic(int sw_control) > +{ > + int retval; > + unsigned long flags; > + > + if (!spin_trylock_irqsave(&pdc_lock, flags)) { > + pr_emerg("Couldn't enable soft power button\n"); > + return -EBUSY; /* ignored by the panic notifier */ > + } > + > + retval =3D mem_pdc_call(PDC_SOFT_POWER, PDC_SOFT_POWER_ENABLE, __pa(pd= c_result), sw_control); > + spin_unlock_irqrestore(&pdc_lock, flags); > + > + return retval; > +} > + > /* > * pdc_io_reset - Hack to avoid overlapping range registers of Bridges = devices. > * Primarily a problem on T600 (which parisc-linux doesn't support) but > diff --git a/drivers/parisc/power.c b/drivers/parisc/power.c > index 456776bd8ee6..8512884de2cf 100644 > --- a/drivers/parisc/power.c > +++ b/drivers/parisc/power.c > @@ -37,7 +37,6 @@ > #include > #include > #include > -#include > #include > #include > #include > @@ -175,16 +174,21 @@ static void powerfail_interrupt(int code, void *x) > > > > -/* parisc_panic_event() is called by the panic handler. > - * As soon as a panic occurs, our tasklets above will not be > - * executed any longer. This function then re-enables the > - * soft-power switch and allows the user to switch off the system > +/* > + * parisc_panic_event() is called by the panic handler. > + * > + * As soon as a panic occurs, our tasklets above will not > + * be executed any longer. This function then re-enables > + * the soft-power switch and allows the user to switch off > + * the system. We rely in pdc_soft_power_button_panic() > + * since this version spin_trylocks (instead of regular > + * spinlock), preventing deadlocks on panic path. > */ > static int parisc_panic_event(struct notifier_block *this, > unsigned long event, void *ptr) > { > /* re-enable the soft-power switch */ > - pdc_soft_power_button(0); > + pdc_soft_power_button_panic(0); > return NOTIFY_DONE; > } > > @@ -193,7 +197,6 @@ static struct notifier_block parisc_panic_block =3D = { > .priority =3D INT_MAX, > }; > > - > static int __init power_init(void) > { > unsigned long ret;