From patchwork Wed Apr 27 22:48:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Guilherme G. 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Piccoli" To: akpm@linux-foundation.org, bhe@redhat.com, pmladek@suse.com, kexec@lists.infradead.org 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> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220427224924.592546-1-gpiccoli@igalia.com> References: <20220427224924.592546-1-gpiccoli@igalia.com> MIME-Version: 1.0 X-Mailman-Approved-At: Thu, 28 Apr 2022 11:34:03 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-hyperv@vger.kernel.org, halves@canonical.com, David Gow , gregkh@linuxfoundation.org, peterz@infradead.org, alejandro.j.jimenez@oracle.com, linux-remoteproc@vger.kernel.org, feng.tang@intel.com, linux-mips@vger.kernel.org, hidehiro.kawai.ez@hitachi.com, sparclinux@vger.kernel.org, will@kernel.org, tglx@linutronix.de, linux-leds@vger.kernel.org, linux-s390@vger.kernel.org, mikelley@microsoft.com, john.ogness@linutronix.de, corbet@lwn.net, paulmck@kernel.org, fabiomirmar@gmail.com, x86@kernel.org, Evan Green , Ard Biesheuvel , mingo@redhat.com, bcm-kernel-feedback-list@broadcom.com, xen-devel@lists.xenproject.org, dyoung@redhat.com, vgoyal@redhat.com, linux-xtensa@linux-xtensa.org, dave.hansen@linux.intel.com, keescook@chromium.org, arnd@arndb.de, linux-pm@vger.kernel.org, coresight@lists.linaro.org, linux-um@lists.infradead.org, rostedt@goodmis.org, rcu@vger.kernel.org, bp@alien8.de, luto@kernel.org, linux-tegra@vger.kernel.org, openipmi-developer@lists.sourceforge.net, andriy.shevchenko@linux.intel.com, senozhatsky@chromium.org, linux-arm-kernel@lists.infradead.org, linux-edac@vger.kernel.org, jgross@suse.com, linux-parisc@vger.kernel.org, netdev@vger.kernel.org, kernel@gpiccoli.net, linux-kernel@vger.kernel.org, stern@rowland.harvard.edu, gpiccoli@igalia.com, d.hatayama@jp.fujitsu.com, mhiramat@kernel.org, kernel-dev@igalia.com, linux-alpha@vger.kernel.org, Julius Werner , vkuznets@redhat.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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