On Fri, Sep 16, 2022, at 10:24 AM, Tomi Valkeinen wrote: > On 15/09/2022 21:49, Arnd Bergmann wrote: >> On Thu, Sep 15, 2022, at 8:17 PM, kernel test robot wrote: >> I think hte problem is that struct dsi_irq_stats is just too >> large, at 776 bytes. The interrupts are disabled during a copy >> from 'dsi->irq_stats' into 'stats'. A trivial workaround would >> avoid the local copy and keep interrupts disabled through >> the entire function so it can operate directly on the source >> data, but that would introduce a longer time with irqs disabled, >> which might be bad as well. >> >> Since this is only called from a debugfs file, and reading that >> file is probably not performance critical itself, maybe >> using kmalloc on the large structure would be best. > > I think that makes sense. I have sent a patch using kmalloc. > > Oddly enough, I was not able to reproduce the warning with my normal > toolchain, gcc-arm-11.2-2022.02-x86_64-arm-none-linux-gnueabihf. I even > reduced the frame size limit to 700, and saw warnings from other places, > but not from omapdrm. I had another look and found that this only happens with CONFIG_INIT_STACK_ALL_PATTERN=y or CONFIG_INIT_STACK_ALL_ZERO=y, which are only available with gcc-12.x or clang. It looks like without that, gcc can reduce the size of the on-stack variable by only copying the members that it actually needs, see https://pastebin.com/8dDRE1bX for the gcc-11 output. Arnd
