# git rev-parse -q --verify ab6f762f0f53162d41497708b33c9a3236d3609e^{commit}
ab6f762f0f53162d41497708b33c9a3236d3609e
already have revision, skipping fetch
# git checkout -q -f -B kisskb ab6f762f0f53162d41497708b33c9a3236d3609e
# git clean -qxdf
# < git log -1
# commit ab6f762f0f53162d41497708b33c9a3236d3609e
# Author: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
# Date:   Tue Mar 3 20:30:02 2020 +0900
# 
#     printk: queue wake_up_klogd irq_work only if per-CPU areas are ready
#     
#     printk_deferred(), similarly to printk_safe/printk_nmi, does not
#     immediately attempt to print a new message on the consoles, avoiding
#     calls into non-reentrant kernel paths, e.g. scheduler or timekeeping,
#     which potentially can deadlock the system.
#     
#     Those printk() flavors, instead, rely on per-CPU flush irq_work to print
#     messages from safer contexts.  For same reasons (recursive scheduler or
#     timekeeping calls) printk() uses per-CPU irq_work in order to wake up
#     user space syslog/kmsg readers.
#     
#     However, only printk_safe/printk_nmi do make sure that per-CPU areas
#     have been initialised and that it's safe to modify per-CPU irq_work.
#     This means that, for instance, should printk_deferred() be invoked "too
#     early", that is before per-CPU areas are initialised, printk_deferred()
#     will perform illegal per-CPU access.
#     
#     Lech Perczak [0] reports that after commit 1b710b1b10ef ("char/random:
#     silence a lockdep splat with printk()") user-space syslog/kmsg readers
#     are not able to read new kernel messages.
#     
#     The reason is printk_deferred() being called too early (as was pointed
#     out by Petr and John).
#     
#     Fix printk_deferred() and do not queue per-CPU irq_work before per-CPU
#     areas are initialized.
#     
#     Link: https://lore.kernel.org/lkml/aa0732c6-5c4e-8a8b-a1c1-75ebe3dca05b@camlintechnologies.com/
#     Reported-by: Lech Perczak <l.perczak@camlintechnologies.com>
#     Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
#     Tested-by: Jann Horn <jannh@google.com>
#     Reviewed-by: Petr Mladek <pmladek@suse.com>
#     Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
#     Cc: Theodore Ts'o <tytso@mit.edu>
#     Cc: John Ogness <john.ogness@linutronix.de>
#     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 ab6f762f0f53162d41497708b33c9a3236d3609e
# < make -s -j 32 ARCH=arm O=/kisskb/build/linus_at91_dt_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-  at91_dt_defconfig
# < make -s -j 32 ARCH=arm O=/kisskb/build/linus_at91_dt_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 32 ARCH=arm O=/kisskb/build/linus_at91_dt_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 32 ARCH=arm O=/kisskb/build/linus_at91_dt_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-  
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c: In function 'drm_dp_mst_dsc_aux_for_port':
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5497:9: warning: missing braces around initializer [-Wmissing-braces]
  struct drm_dp_desc desc = { 0 };
         ^
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5497:9: warning: (near initialization for 'desc.ident') [-Wmissing-braces]
Completed OK
# rm -rf /kisskb/build/linus_at91_dt_defconfig_arm-gcc4.9
# Build took: 0:01:21.479682