# git rev-parse -q --verify ee40d543e97d23d3392d8fb1ec9972eb4e9c7611^{commit}
ee40d543e97d23d3392d8fb1ec9972eb4e9c7611
already have revision, skipping fetch
# git checkout -q -f -B kisskb ee40d543e97d23d3392d8fb1ec9972eb4e9c7611
# git clean -qxdf
# < git log -1
# commit ee40d543e97d23d3392d8fb1ec9972eb4e9c7611
# Author: Hugh Dickins <hughd@google.com>
# Date:   Sat Sep 2 08:29:30 2023 -0700
# 
#     mm/pagewalk: fix bootstopping regression from extra pte_unmap()
#     
#     Mikhail reports early-6.6-based Fedora Rawhide not booting: "rcu_preempt
#     detected expedited stalls", minutes wait, and then hung_task splat while
#     kworker trying to synchronize_rcu_expedited().  Nothing logged to disk.
#     
#     He bisected to my 6.6 a349d72fd9ef ("mm/pgtable: add rcu_read_lock() and
#     rcu_read_unlock()s"): but the one to blame is my 6.5 commit to fix the
#     espfix "bad pmd" warnings when booting x86_64 with CONFIG_EFI_PGT_DUMP=y.
#     
#     Gaah, that added an "addr >= TASK_SIZE" check to avoid pte_offset_map(),
#     but failed to add the equivalent check when choosing to pte_unmap().
#     
#     It's not a problem on 6.5 (for different reasons, it's harmless on both
#     64-bit and 32-bit), but becomes a bootstopper on 6.6 with the unbalanced
#     rcu_read_unlock() - RCU has a WARN_ON_ONCE for that, but it would have
#     scrolled off Mikhail's console too quickly.
#     
#     Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
#     Closes: https://lore.kernel.org/linux-mm/CABXGCsNi8Tiv5zUPNXr6UJw6qV1VdaBEfGqEAMkkXE3QPvZuAQ@mail.gmail.com/
#     Fixes: 8b1cb4a2e819 ("mm/pagewalk: fix EFI_PGT_DUMP of espfix area")
#     Fixes: a349d72fd9ef ("mm/pgtable: add rcu_read_lock() and rcu_read_unlock()s")
#     Signed-off-by: Hugh Dickins <hughd@google.com>
#     Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-ld --version
# < git log --format=%s --max-count=1 ee40d543e97d23d3392d8fb1ec9972eb4e9c7611
# make -s -j 32 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  x86_64_defconfig
# < make -s -j 32 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  help
# make -s -j 32 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  olddefconfig
# make -s -j 32 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/x86_64-linux/bin/x86_64-linux-  
Completed OK
# rm -rf /kisskb/build/linus_x86_64_defconfig_x86_64-gcc8
# Build took: 0:02:07.731363