On Saturday 30 April 2016 21:14:49 Matt Fleming wrote: > On Fri, 29 Apr, at 07:48:31PM, Arnd Bergmann wrote: > > gcc complains about a newly added file for the EFI Bootloader Control: > > > > drivers/firmware/efi/efibc.c: In function 'efibc_set_variable': > > drivers/firmware/efi/efibc.c:53:1: error: the frame size of 2272 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] > > > > The problem is the declaration of a local variable of type > > struct efivar_entry, which is by itself larger than the warning > > limit of 1024 bytes. > > > > We know that the reboot notifiers are not called from a deep stack, > > so this is not an actual bug, but we should still try to rework > > the code to avoid the warning. We also know that reboot notifiers > > are never run concurrently on multiple CPUs, so there is no problem > > in just making the variable 'static'. > > I assumed reboot notifiers were guaranteed to be non-concurrent too > but having dug into the callers of kernel_reboot(), I couldn't find > any kind of mutual exclusion. > > How/where is this guaranteed? The sys_restart() system call takes a mutex before calling kernel_restart() or kernel_poweroff(). I've had a closer look now and found that there are a few other callers of kernel_restart, so I guess if you restart using sysctl at the exact same time as calling /sbin/reboot, things may break. It's not something we'd have to worry about in practice, but it does make my patch incorrect. Should we come up with a different way to do it? Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
