On Mon, Oct 17, 2022 at 11:00:46AM -0300, Guilherme G. Piccoli wrote: > On 18/09/2022 10:58, Guilherme G. Piccoli wrote: > > On 19/08/2022 19:17, Guilherme G. Piccoli wrote: > >> Currently the regular CPU shutdown path for ARM disables IRQs/FIQs > >> in the secondary CPUs - smp_send_stop() calls ipi_cpu_stop(), which > >> is responsible for that. IRQs are architecturally masked when we > >> take an interrupt, but FIQs are high priority than IRQs, hence they > >> aren't masked. With that said, it makes sense to disable FIQs here, > >> but there's no need for (re-)disabling IRQs. > >> > >> More than that: there is an alternative path for disabling CPUs, > >> in the form of function crash_smp_send_stop(), which is used for > >> kexec/panic path. This function relies on a SMP call that also > >> triggers a busy-wait loop [at machine_crash_nonpanic_core()], but > >> without disabling FIQs. This might lead to odd scenarios, like > >> early interrupts in the boot of kexec'd kernel or even interrupts > >> in secondary "disabled" CPUs while the main one still works in the > >> panic path and assumes all secondary CPUs are (really!) off. > >> > >> So, let's disable FIQs in both paths and *not* disable IRQs a second > >> time, since they are already masked in both paths by the architecture. > >> This way, we keep both CPU quiesce paths consistent and safe. > >> > >> Cc: Marc Zyngier <maz@xxxxxxxxxx> > >> Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx> > >> Cc: Russell King <linux@xxxxxxxxxxxxxxx> > >> Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx> > >> > > Monthly ping - let me know if there's something I should improve in > order this fix is considered! Patches don't get applied unless they end up in the patch system. Thanks. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
