# git rev-parse -q --verify 3c53776e29f81719efcf8f7a6e30cdf753bee94d^{commit}
3c53776e29f81719efcf8f7a6e30cdf753bee94d
already have revision, skipping fetch
# git checkout -q -f -B kisskb 3c53776e29f81719efcf8f7a6e30cdf753bee94d
# git clean -qxdf
# < git log -1
# commit 3c53776e29f81719efcf8f7a6e30cdf753bee94d
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Mon Jan 8 11:51:04 2018 -0800
# 
#     Mark HI and TASKLET softirq synchronous
#     
#     Way back in 4.9, we committed 4cd13c21b207 ("softirq: Let ksoftirqd do
#     its job"), and ever since we've had small nagging issues with it.  For
#     example, we've had:
#     
#       1ff688209e2e ("watchdog: core: make sure the watchdog_worker is not deferred")
#       8d5755b3f77b ("watchdog: softdog: fire watchdog even if softirqs do not get to run")
#       217f69743681 ("net: busy-poll: allow preemption in sk_busy_loop()")
#     
#     all of which worked around some of the effects of that commit.
#     
#     The DVB people have also complained that the commit causes excessive USB
#     URB latencies, which seems to be due to the USB code using tasklets to
#     schedule USB traffic.  This seems to be an issue mainly when already
#     living on the edge, but waiting for ksoftirqd to handle it really does
#     seem to cause excessive latencies.
#     
#     Now Hanna Hawa reports that this issue isn't just limited to USB URB and
#     DVB, but also causes timeout problems for the Marvell SoC team:
#     
#      "I'm facing kernel panic issue while running raid 5 on sata disks
#       connected to Macchiatobin (Marvell community board with Armada-8040
#       SoC with 4 ARMv8 cores of CA72) Raid 5 built with Marvell DMA engine
#       and async_tx mechanism (ASYNC_TX_DMA [=y]); the DMA driver (mv_xor_v2)
#       uses a tasklet to clean the done descriptors from the queue"
#     
#     The latency problem causes a panic:
#     
#       mv_xor_v2 f0400000.xor: dma_sync_wait: timeout!
#       Kernel panic - not syncing: async_tx_quiesce: DMA error waiting for transaction
#     
#     We've discussed simply just reverting the original commit entirely, and
#     also much more involved solutions (with per-softirq threads etc).  This
#     patch is intentionally stupid and fairly limited, because the issue
#     still remains, and the other solutions either got sidetracked or had
#     other issues.
#     
#     We should probably also consider the timer softirqs to be synchronous
#     and not be delayed to ksoftirqd (since they were the issue with the
#     earlier watchdog problems), but that should be done as a separate patch.
#     This does only the tasklet cases.
#     
#     Reported-and-tested-by: Hanna Hawa <hannah@marvell.com>
#     Reported-and-tested-by: Josef Griebichler <griebichler.josef@gmx.at>
#     Reported-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
#     Cc: Alan Stern <stern@rowland.harvard.edu>
#     Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
#     Cc: Eric Dumazet <edumazet@google.com>
#     Cc: Ingo Molnar <mingo@kernel.org>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-gcc --version
# < git log --format=%s --max-count=1 3c53776e29f81719efcf8f7a6e30cdf753bee94d
# < make -s -j 48 ARCH=mips O=/kisskb/build/linus_mips-defconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  defconfig
# make -s -j 48 ARCH=mips O=/kisskb/build/linus_mips-defconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  
/kisskb/src/arch/mips/vdso/Makefile:32: MIPS VDSO requires binutils >= 2.25
/kisskb/src/arch/mips/vdso/Makefile:32: MIPS VDSO requires binutils >= 2.25
/kisskb/src/kernel/rcu/srcutree.c: In function 'init_srcu_struct_fields':
/kisskb/src/kernel/rcu/srcutree.c:146:32: warning: 'levelspread[<Ue960>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:94:6: note: 'levelspread[<Ue960>]' was declared here
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/cgroup/cgroup-v1.c: In function 'cgroup1_mount':
/kisskb/src/kernel/cgroup/cgroup-v1.c:1256:20: warning: 'root' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:339:21: note: 'pdeo' was declared here
/kisskb/src/drivers/base/regmap/regmap.c: In function '_regmap_raw_write':
/kisskb/src/drivers/base/regmap/regmap.c:1819:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/base/regmap/regmap.c: In function 'regmap_raw_read':
/kisskb/src/drivers/base/regmap/regmap.c:2497:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/tty/serial/8250/8250_core.c: In function 'univ8250_release_irq':
/kisskb/src/drivers/tty/serial/8250/8250_core.c:251:18: warning: 'i' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/tty/serial/8250/8250_core.c:231:19: note: 'i' was declared here
/kisskb/src/arch/mips/vdso/Makefile:32: MIPS VDSO requires binutils >= 2.25
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
FIT description: Linux 4.18.0-rc5-g3c53776
Created:         Wed Jul 18 11:57:00 2018
 Image 0 (kernel@0)
  Description:  Linux 4.18.0-rc5-g3c53776
  Created:      Wed Jul 18 11:57:00 2018
  Type:         Kernel Image
  Compression:  gzip compressed
  Data Size:    4338107 Bytes = 4236.43 kB = 4.14 MB
  Architecture: MIPS
  OS:           Linux
  Load Address: 0x80100000
  Entry Point:  0x80830df0
  Hash algo:    sha1
  Hash value:   da3a748069cadb624af43aba7a16a249f5efa0cb
 Image 1 (fdt@boston)
  Description:  img,boston Device Tree
  Created:      Wed Jul 18 11:57:00 2018
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    3668 Bytes = 3.58 kB = 0.00 MB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   569c37cc891ce1e1f3a193cb41cc691a5d2debb5
 Image 2 (fdt@ni169445)
  Description:  NI 169445 device tree
  Created:      Wed Jul 18 11:57:00 2018
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    1871 Bytes = 1.83 kB = 0.00 MB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   51b89b31605ee62038c8468c429af091dfc75ec7
 Image 3 (fdt@xilfpga)
  Description:  MIPSfpga (xilfpga) Device Tree
  Created:      Wed Jul 18 11:57:00 2018
  Type:         Flat Device Tree
  Compression:  uncompressed
  Data Size:    2708 Bytes = 2.64 kB = 0.00 MB
  Architecture: MIPS
  Hash algo:    sha1
  Hash value:   509ce58e44c561d54539e64e9d4b47054e696fc6
 Default Configuration: 'conf@default'
 Configuration 0 (conf@default)
  Description:  Generic Linux kernel
  Kernel:       kernel@0
 Configuration 1 (conf@boston)
  Description:  Boston Linux kernel
  Kernel:       kernel@0
  FDT:          fdt@boston
 Configuration 2 (conf@ni169445)
  Description:  NI 169445 Linux Kernel
  Kernel:       kernel@0
  FDT:          fdt@ni169445
 Configuration 3 (conf@xilfpga)
  Description:  MIPSfpga Linux kernel
  Kernel:       kernel@0
  FDT:          fdt@xilfpga
Completed OK
# rm -rf /kisskb/build/linus_mips-defconfig_mips
# Build took: 0:01:25.066193