From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guilherme G. Piccoli Date: Wed, 27 Apr 2022 19:48:58 -0300 Subject: [PATCH 04/30] firmware: google: Convert regular spinlock into trylock on panic path In-Reply-To: <20220427224924.592546-1-gpiccoli@igalia.com> References: <20220427224924.592546-1-gpiccoli@igalia.com> Message-ID: <20220427224924.592546-5-gpiccoli@igalia.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kexec@lists.infradead.org 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