Hi Rafal, On Mon, Aug 7, 2023 at 1:11 PM Rafał Miłecki <zaj...@gmail.com> wrote: > On 4.08.2023 13:07, Rafał Miłecki wrote: > > I triple checked that. Dropping a single unused function breaks kernel / > > device stability on BCM53573! > > > > AFAIK the only thing below diff actually affects is location of symbols > > (I actually verified that by comparing System.map before and after - > > over 22'000 of relocated symbols). > > > > Can some unfortunate location of symbols cause those hangs/lockups? > > I performed another experiment. First I dropped mtd_check_of_node() to > bring kernel back to the stable state. > > Then I started adding useless code to the mtdchar_unlocked_ioctl(). I > ended up adding just enough to make sure all post-mtd symbols in > System.map got the same offset as in case of backporting > mtd_check_of_node(). > > I started experiencing lockups/hangs again. > > I repeated the same test with adding dumb code to the brcm_nvram_probe() > and verifying symbols offsets following brcm_nvram_probe one. > > I believe this confirms that this problem is about offset or alignment > of some specific symbol(s). The remaining question is what symbols and > how to fix or workaround that.
I had similar experiences on other ARM platforms many years ago: bisection lead to something completely bogus, and it turned out adding a single line of innocent code made the system lock-up or crash unexpectedly. It was definitely related to alignment, as adding the right extra amount of innocent code would fix the problem. Until some later change changing alignment again... I never found the real cause, but the problems went away over time. I am not sure I did enable all required errata config options, so I may have missed some... Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/mailman/listinfo/openwrt-devel