From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Guilherme G. Piccoli" Subject: [PATCH 04/30] firmware: google: Convert regular spinlock into trylock on panic path Date: Wed, 27 Apr 2022 19:48:58 -0300 Message-ID: <20220427224924.592546-5-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=6uCmJtZx2tt75N7rOkxcF9GqtQGKdOCOB58J9Fug6qk=; b=DsA3q7/djrGRVf zMXteEWV417X/UFAJcU0zubjAELfsjiSkE6klaxcNuZM0MAr8EaxEeRPQ6ntJxpVx9IedwBOfsdla wOdlClSqR1hNxBv0barkIhUE5xxRZRiLZyCeMedBcA5QNM++YvS3YtdoWRRShBZHvjB6vs4QDL+a6 U7XfEXzvq9+6sWyti5j+v/i9Nc8gnQsXflFUmfBQHf6O9hoIjym5nfOqtAfY+efaruhEV236BiFby CY29cQOztkw2y5yLYBpvJzgT6o1nOHkgvoAwhx5bDwKfPssL36JKLA2jfa/3qIfreptzzHbtpGElm LcGAafD3wEohbFmE8JAA==; 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=s8xeHJYGrg2PKjTPKivxQn37LuEP6tnBzN9Ru5ARxEw=; b=itLofTxVD3jMCMG1QHrJKsVczn vbwUlm+NWg0pMSOCtSjWETMXDXA/dO9ti0V72q001TMmb2gIzR2yZduw7qvMkCQ0akMjJfPi2/PQc iUqIhedKtPpwa0f3Qs25a8tdm2oshD1/KMZCL+mdxqH7vtpZXZFld+eSj+8owBfmLjMNmktzOqSfY dTb/ic9+j716feaFlMGDFCnVL8lNNI9bMH1gzqsKPsNg72iLmPQmwnJD7EfxHW7NQoAv8T+6Y8VEH 2ohazyjoc9Z+MNXm7Lr7Bh3GLxJ6zmDCTC3SRdi9P8jirAP5MyZi4cLioUm7IG4Ag3/IwiKZ9+K4K 3P27PVmg==; 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. Currently the gsmi driver registers a panic notifier as well as reboot and die notifiers. The callbacks registered are called in atomic and very limited context - for instance, panic disables preemption, local IRQs and all other CPUs that aren't running the current panic function. With that said, taking a spinlock in this scenario is a dangerous invitation for a deadlock scenario. So, we fix that in this commit by changing the regular spinlock with a trylock, which is a safer approach. Fixes: 74c5b31c6618 ("driver: Google EFI SMI") Cc: Ard Biesheuvel Cc: David Gow Cc: Evan Green Cc: Julius Werner Signed-off-by: Guilherme G. Piccoli --- drivers/firmware/google/gsmi.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c index adaa492c3d2d..b01ed02e4a87 100644 --- a/drivers/firmware/google/gsmi.c +++ b/drivers/firmware/google/gsmi.c @@ -629,7 +629,10 @@ static int gsmi_shutdown_reason(int reason) if (saved_reason & (1 << reason)) return 0; - spin_lock_irqsave(&gsmi_dev.lock, flags); + if (!spin_trylock_irqsave(&gsmi_dev.lock, flags)) { + rc = -EBUSY; + goto out; + } saved_reason |= (1 << reason); @@ -646,6 +649,7 @@ static int gsmi_shutdown_reason(int reason) spin_unlock_irqrestore(&gsmi_dev.lock, flags); +out: if (rc < 0) printk(KERN_ERR "gsmi: Log Shutdown Reason failed\n"); else -- 2.36.0