# git rev-parse -q --verify 625d3449788f85569096780592549d0340e9c0c7^{commit}
625d3449788f85569096780592549d0340e9c0c7
already have revision, skipping fetch
# 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-8.1.0-nolibc/m68k-linux/bin/m68k-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-ld --version
# < git log --format=%s --max-count=1 625d3449788f85569096780592549d0340e9c0c7
# < make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  m5272c3_defconfig
# < make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  help
# make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  olddefconfig
# make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-  
/kisskb/src/drivers/net/ethernet/freescale/fec_main.c: In function 'fec_restart':
/kisskb/src/drivers/net/ethernet/freescale/fec_main.c:949:6: warning: unused variable 'val' [-Wunused-variable]
  u32 val;
      ^~~
/kisskb/src/drivers/net/ethernet/freescale/fec_main.c: In function 'fec_get_mac':
/kisskb/src/drivers/net/ethernet/freescale/fec_main.c:1692:28: warning: unused variable 'pdata' [-Wunused-variable]
  struct fec_platform_data *pdata = dev_get_platdata(&fep->pdev->dev);
                            ^~~~~
In file included from /kisskb/src/arch/m68k/include/asm/atomic.h:7,
                 from /kisskb/src/include/linux/atomic.h:7,
                 from /kisskb/src/include/linux/spinlock.h:460,
                 from /kisskb/src/include/linux/seqlock.h:36,
                 from /kisskb/src/include/linux/time.h:6,
                 from /kisskb/src/include/linux/stat.h:19,
                 from /kisskb/src/include/linux/module.h:13,
                 from /kisskb/src/net/core/filter.c:20:
/kisskb/src/net/core/filter.c: In function 'bpf_clear_redirect_map':
/kisskb/src/arch/m68k/include/asm/cmpxchg.h:137:3: warning: value computed is not used [-Wunused-value]
  ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
  ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    (unsigned long)(n), sizeof(*(ptr))))
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/kisskb/src/include/asm-generic/cmpxchg.h:106:28: note: in expansion of macro 'cmpxchg_local'
 #define cmpxchg(ptr, o, n) cmpxchg_local((ptr), (o), (n))
                            ^~~~~~~~~~~~~
/kisskb/src/net/core/filter.c:3569:4: note: in expansion of macro 'cmpxchg'
    cmpxchg(&ri->map, map, NULL);
    ^~~~~~~
Completed OK
# rm -rf /kisskb/build/linus_m5272c3_defconfig_m68k-gcc8
# Build took: 0:00:29.192346