# 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 # 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 # Reported-and-tested-by: Josef Griebichler # Reported-by: Mauro Carvalho Chehab # Cc: Alan Stern # Cc: Greg Kroah-Hartman # Cc: Eric Dumazet # Cc: Ingo Molnar # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-gcc --version # < git log --format=%s --max-count=1 3c53776e29f81719efcf8f7a6e30cdf753bee94d # < make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- randconfig KCONFIG_SEED=0xFE7679FB # Added to kconfig CONFIG_STANDALONE=y # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_MODULE_SIG=n # Added to kconfig CONFIG_CPU_BIG_ENDIAN=y # Added to kconfig CONFIG_PPC64=y # Added to kconfig CONFIG_PPC_DISABLE_WERROR=y # Added to kconfig CONFIG_SECTION_MISMATCH_WARN_ONLY=y # Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y # Added to kconfig CONFIG_CC_STACKPROTECTOR_STRONG=n # Added to kconfig CONFIG_GCC_PLUGINS=n # Added to kconfig CONFIG_LD_HEAD_STUB_CATCH=y # Added to kconfig # yes \n | make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- oldconfig yes: standard output: Broken pipe yes: write error # make -s -j 48 ARCH=powerpc O=/kisskb/build/linus-rand_powerpc-randconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- In file included from /kisskb/src/arch/powerpc/xmon/xmon.c:66:0: /kisskb/src/arch/powerpc/xmon/dis-asm.h: In function 'print_insn_powerpc': /kisskb/src/arch/powerpc/xmon/dis-asm.h:20:2: warning: format '%x' expects argument of type 'unsigned int', but argument 2 has type 'long unsigned int' [-Wformat] /kisskb/src/arch/powerpc/xmon/dis-asm.h: In function 'print_insn_spu': /kisskb/src/arch/powerpc/xmon/dis-asm.h:26:2: warning: format '%x' expects argument of type 'unsigned int', but argument 2 has type 'long unsigned int' [-Wformat] /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/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/sound/soc/codecs/da7219-aad.c: In function 'da7219_aad_hptest_work': /kisskb/src/sound/soc/codecs/da7219-aad.c:318:17: warning: 'pll_ctrl' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/dma-buf/reservation.c: In function 'reservation_object_add_shared_fence': /kisskb/src/drivers/dma-buf/reservation.c:207:2: warning: 'k' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/dma-buf/reservation.c:160:17: note: 'k' was declared here /kisskb/src/sound/soc/codecs/wm8960.c: In function 'wm8960_configure_clocking': /kisskb/src/sound/soc/codecs/wm8960.c:803:70: warning: 'j' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/sound/soc/codecs/wm8960.c:800:68: warning: 'i' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/mfd/arizona-core.c: In function 'arizona_dev_init': /kisskb/src/drivers/mfd/arizona-core.c:1404:6: warning: 'n_subdevs' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/iio/temperature/mlx90632.c: In function 'mlx90632_read_raw': /kisskb/src/drivers/iio/temperature/mlx90632.c:348:37: warning: 'object_old_raw' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/iio/temperature/mlx90632.c:429:56: note: 'object_old_raw' was declared here /kisskb/src/drivers/iio/temperature/mlx90632.c:348:37: warning: 'object_new_raw' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/iio/temperature/mlx90632.c:429:40: note: 'object_new_raw' was declared here WARNING: 4 bad relocations c000000000028726 R_PPC64_ADDR16_HIGHEST .head.text+0x0000000000028740 c00000000002872a R_PPC64_ADDR16_HIGHER .head.text+0x0000000000028740 c000000000028732 R_PPC64_ADDR16_HI .head.text+0x0000000000028740 c000000000028736 R_PPC64_ADDR16_LO .head.text+0x0000000000028740 Completed OK # rm -rf /kisskb/build/linus-rand_powerpc-randconfig_powerpc # Build took: 0:01:16.117227