# git rev-parse -q --verify 625d3449788f85569096780592549d0340e9c0c7^{commit}
# git fetch -q -n -f git://fs.ozlabs.ibm.com/kernel/linus master
# git rev-parse -q --verify 625d3449788f85569096780592549d0340e9c0c7^{commit}
625d3449788f85569096780592549d0340e9c0c7
# git checkout -q -f -B kisskb 625d3449788f85569096780592549d0340e9c0c7
# git clean -qxdf
# < git log -1
# commit 625d3449788f85569096780592549d0340e9c0c7
# Author: Jason A. Donenfeld <Jason@zx2c4.com>
# Date:   Sun Jun 21 21:02:22 2020 -0600
# 
#     Revert "kernel/printk: add kmsg SEEK_CUR handling"
#     
#     This reverts commit 8ece3b3eb576a78d2e67ad4c3a80a39fa6708809.
#     
#     This commit broke userspace. Bash uses ESPIPE to determine whether or
#     not the file should be read using "unbuffered I/O", which means reading
#     1 byte at a time instead of 128 bytes at a time. I used to use bash to
#     read through kmsg in a really quite nasty way:
#     
#         while read -t 0.1 -r line 2>/dev/null || [[ $? -ne 142 ]]; do
#            echo "SARU $line"
#         done < /dev/kmsg
#     
#     This will show all lines that can fit into the 128 byte buffer, and skip
#     lines that don't. That's pretty awful, but at least it worked.
#     
#     With this change, bash now tries to do 1-byte reads, which means it
#     skips all the lines, which is worse than before.
#     
#     Now, I don't really care very much about this, and I'm already look for
#     a workaround. But I did just spend an hour trying to figure out why my
#     scripts were broken. Either way, it makes no difference to me personally
#     whether this is reverted, but it might be something to consider. If you
#     declare that "trying to read /dev/kmsg with bash is terminally stupid
#     anyway," I might be inclined to agree with you. But do note that bash
#     uses lseek(fd, 0, SEEK_CUR)==>ESPIPE to determine whether or not it's
#     reading from a pipe.
#     
#     Cc: Bruno Meneguele <bmeneg@redhat.com>
#     Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
#     Cc: Steven Rostedt <rostedt@goodmis.org>
#     Cc: David Laight <David.Laight@ACULAB.COM>
#     Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
#     Cc: Petr Mladek <pmladek@suse.com>
#     Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-gcc --version
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-ld --version
# < git log --format=%s --max-count=1 625d3449788f85569096780592549d0340e9c0c7
# < make -s -j 10 ARCH=arm O=/kisskb/build/linus_lpd270_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-  lpd270_defconfig
# < make -s -j 10 ARCH=arm O=/kisskb/build/linus_lpd270_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-  help
# make -s -j 10 ARCH=arm O=/kisskb/build/linus_lpd270_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-  olddefconfig
# make -s -j 10 ARCH=arm O=/kisskb/build/linus_lpd270_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-  
Completed OK
# rm -rf /kisskb/build/linus_lpd270_defconfig_arm-gcc4.9
# Build took: 0:01:57.729759