From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Guilherme G. Piccoli" Subject: [PATCH 12/30] parisc: Replace regular spinlock with spin_trylock on panic path Date: Wed, 27 Apr 2022 19:49:06 -0300 Message-ID: <20220427224924.592546-13-gpiccoli@igalia.com> References: <20220427224924.592546-1-gpiccoli@igalia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=tK2WXPkYdcLyPSLrvUWqOYatykV2GaGMdBAfJiXsyDI=; b=sEdmU2uh4wSW4g JzPbrICP8aVhSvzXEOi9wbi6jgTH58XzqHMEmtXEngsLH1DIf11bqX2anb1PwRVuvFAnilCJ0zHmF zGXPjtdUOeaNiiI2MhUysygXz2Zbo4Tzy4L7tkG9QVymcVkIUmZp4g68PlIH9r98jGbNxDbMijslm wlA4bT9zQ1uBipZrFSHnppt+rqezfvTU8JvrrQAjI5p83Vdr58tECyXL2QWPj07FIcsICW1Of0dVG MwFxWZZ0IdB757BUXzNLw+r8jkw8FmP2KmDC2ULcqpERuJV4vAD/iT61NJPuGUfACig8WEK4h8c0n fdq880lfqz+nLijwdtiA==; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=Kr032SD5vU+3986AqF/gyJuhFfnr0rncUaszbIKwr2Y=; b=fBwyO/j+yxT2AymE7SizsCmDjX 1r+REb2uiNLyOmmbv6Nh9J6FxLhB1bfvTpTjG3mgSTFTL8dz34enGcBQdaqLpKSF+I5gGd/nAJUMJ jfyQZXSy1JqEja03OmP72YQEOLiC8m3Lw1UsxeNTdyoogn1QFWiKLBkCPwl7A/i8ZlFDdHuwQzMA1 jTKSmHNDM3VElo6fZPijCzvlYComyxyp1IGRSiaeBrih1Typo5NHSl5Gp5sEACObYkVVo4g3YPBCY BcFTyK5zLHDJeUb/agfenHI/ZzcT83HZfKlj9EnBYJpw9rKnDjMmdBRtHu3w1BfvP2PQydzd7nH74 efngoTDg==; In-Reply-To: <20220427224924.592546-1-gpiccoli@igalia.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+glud-user-mode-linux-devel=m.gmane-mx.org@lists.infradead.org To: 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, gpiccoli@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. 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 --- 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 *power_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 behaviour + * @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 = mem_pdc_call(PDC_SOFT_POWER, PDC_SOFT_POWER_ENABLE, __pa(pdc_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 = { .priority = INT_MAX, }; - static int __init power_init(void) { unsigned long ret; -- 2.36.0