# git rev-parse -q --verify 8ca09d5fa3549d142c2080a72a4c70ce389163cd^{commit}
8ca09d5fa3549d142c2080a72a4c70ce389163cd
already have revision, skipping fetch
# git checkout -q -f -B kisskb 8ca09d5fa3549d142c2080a72a4c70ce389163cd
# git clean -qxdf
# < git log -1
# commit 8ca09d5fa3549d142c2080a72a4c70ce389163cd
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Mon Mar 6 12:15:13 2023 -0800
# 
#     cpumask: fix incorrect cpumask scanning result checks
#     
#     It turns out that commit 596ff4a09b89 ("cpumask: re-introduce
#     constant-sized cpumask optimizations") exposed a number of cases of
#     drivers not checking the result of "cpumask_next()" and friends
#     correctly.
#     
#     The documented correct check for "no more cpus in the cpumask" is to
#     check for the result being equal or larger than the number of possible
#     CPU ids, exactly _because_ we've always done those constant-sized
#     cpumask scans using a widened type before.  So the return value of a
#     cpumask scan should be checked with
#     
#             if (cpu >= nr_cpu_ids)
#                     ...
#     
#     because the cpumask scan did not necessarily stop exactly *at* that
#     maximum CPU id.
#     
#     But a few cases ended up instead using checks like
#     
#             if (cpu == nr_cpumask_bits)
#                     ...
#     
#     which used that internal "widened" number of bits.  And that used to
#     work pretty much by accident (ok, in this case "by accident" is simply
#     because it matched the historical internal implementation of the cpumask
#     scanning, so it was more of a "intentionally using implementation
#     details rather than an accident").
#     
#     But the extended constant-sized optimizations then did that internal
#     implementation differently, and now that code that did things wrong but
#     matched the old implementation no longer worked at all.
#     
#     Which then causes subsequent odd problems due to using what ends up
#     being an invalid CPU ID.
#     
#     Most of these cases require either unusual hardware or special uses to
#     hit, but the random.c one triggers quite easily.
#     
#     All you really need is to have a sufficiently small CONFIG_NR_CPUS value
#     for the bit scanning optimization to be triggered, but not enough CPUs
#     to then actually fill that widened cpumask.  At that point, the cpumask
#     scanning will return the NR_CPUS constant, which is _not_ the same as
#     nr_cpumask_bits.
#     
#     This just does the mindless fix with
#     
#        sed -i 's/== nr_cpumask_bits/>= nr_cpu_ids/'
#     
#     to fix the incorrect uses.
#     
#     The ones in the SCSI lpfc driver in particular could probably be fixed
#     more cleanly by just removing that repeated pattern entirely, but I am
#     not emptionally invested enough in that driver to care.
#     
#     Reported-and-tested-by: Guenter Roeck <linux@roeck-us.net>
#     Link: https://lore.kernel.org/lkml/481b19b5-83a0-4793-b4fd-194ad7b978c3@roeck-us.net/
#     Reported-and-tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
#     Link: https://lore.kernel.org/lkml/CAMuHMdUKo_Sf7TjKzcNDa8Ve+6QrK+P8nSQrSQ=6LTRmcBKNww@mail.gmail.com/
#     Reported-by: Vernon Yang <vernon2gm@gmail.com>
#     Link: https://lore.kernel.org/lkml/20230306160651.2016767-1-vernon2gm@gmail.com/
#     Cc: Yury Norov <yury.norov@gmail.com>
#     Cc: Jason A. Donenfeld <Jason@zx2c4.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-11.3.0-nolibc/aarch64-linux/bin/aarch64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-11.3.0-nolibc/aarch64-linux/bin/aarch64-linux-ld --version
# < git log --format=%s --max-count=1 8ca09d5fa3549d142c2080a72a4c70ce389163cd
# < make -s -j 32 ARCH=arm64 O=/kisskb/build/linus_arm64-allnoconfig_arm64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/aarch64-linux/bin/aarch64-linux-  allnoconfig
# < make -s -j 32 ARCH=arm64 O=/kisskb/build/linus_arm64-allnoconfig_arm64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/aarch64-linux/bin/aarch64-linux-  help
# make -s -j 32 ARCH=arm64 O=/kisskb/build/linus_arm64-allnoconfig_arm64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/aarch64-linux/bin/aarch64-linux-  olddefconfig
# make -s -j 32 ARCH=arm64 O=/kisskb/build/linus_arm64-allnoconfig_arm64-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/aarch64-linux/bin/aarch64-linux-  
Completed OK
# rm -rf /kisskb/build/linus_arm64-allnoconfig_arm64-gcc11
# Build took: 0:00:29.419752