# 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/x86_64-linux/bin/x86_64-linux-gcc --version # < git log --format=%s --max-count=1 3c53776e29f81719efcf8f7a6e30cdf753bee94d # < make -s -j 8 ARCH=x86_64 O=/kisskb/build/linus-rand_x86_64-randconfig_x86_64 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/x86_64-linux/bin/x86_64-linux- randconfig KCONFIG_SEED=0xA7B0737C # Added to kconfig CONFIG_STANDALONE=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_GCC_PLUGIN_CYC_COMPLEXITY=n # Added to kconfig CONFIG_GCC_PLUGIN_SANCOV=n # Added to kconfig CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n # yes \n | make -s -j 8 ARCH=x86_64 O=/kisskb/build/linus-rand_x86_64-randconfig_x86_64 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/x86_64-linux/bin/x86_64-linux- oldconfig yes: standard output: Broken pipe yes: write error # make -s -j 8 ARCH=x86_64 O=/kisskb/build/linus-rand_x86_64-randconfig_x86_64 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/x86_64-linux/bin/x86_64-linux- /kisskb/src/arch/x86/kernel/apic/io_apic.c: In function 'mp_map_pin_to_irq': /kisskb/src/arch/x86/kernel/apic/io_apic.c:1033:6: warning: 'irq' may be used uninitialized in this function [-Wuninitialized] /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/arch/x86/kernel/e820.c: In function 'e820__setup_pci_gap': /kisskb/src/arch/x86/kernel/e820.c:653:2: warning: 'gapstart' may be used uninitialized in this function [-Wuninitialized] kernel/rcu/tree.o: warning: objtool: rcu_init_geometry()+0x65: unreachable instruction /kisskb/src/arch/x86/kernel/hw_breakpoint.c: In function 'arch_validate_hwbkpt_settings': /kisskb/src/arch/x86/kernel/hw_breakpoint.c:361:20: warning: 'align' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/mm/hugetlb.c: In function 'alloc_pool_huge_page': /kisskb/src/mm/hugetlb.c:1433:5: warning: 'page' 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/fs/f2fs/file.c: In function 'f2fs_precache_extents': /kisskb/src/fs/f2fs/file.c:2823:6: warning: 'err' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/lib/raid6/recov_avx512.c:387:2: warning: #warning "your version of binutils lacks AVX512 support" [-Wcpp] /kisskb/src/lib/raid6/recov_avx512.c:387:2: warning: #warning "your version of binutils lacks AVX512 support" [-Wcpp] /kisskb/src/fs/f2fs/node.c: In function '__set_nat_cache_dirty': /kisskb/src/include/linux/list.h:63:13: warning: 'head' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/f2fs/node.c:225:24: note: 'head' was declared here /kisskb/src/fs/f2fs/sysfs.c:519:12: warning: 'segment_info_seq_show' defined but not used [-Wunused-function] /kisskb/src/fs/f2fs/sysfs.c:546:12: warning: 'segment_bits_seq_show' defined but not used [-Wunused-function] /kisskb/src/fs/f2fs/sysfs.c:570:12: warning: 'iostat_info_seq_show' defined but not used [-Wunused-function] /kisskb/src/drivers/clk/sunxi-ng/ccu_mux.c: In function 'ccu_mux_helper_determine_rate': /kisskb/src/drivers/clk/sunxi-ng/ccu_mux.c:153:22: warning: 'best_parent' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/dma-buf/reservation.c: In function 'reservation_object_add_shared_replace': /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:210:7: warning: 'i' may be used uninitialized in this function [-Wuninitialized] drivers/clk/clk.o: warning: objtool: clk_prepare_unlock()+0x44: unreachable instruction /kisskb/src/drivers/firmware/google/coreboot_table.c: In function 'coreboot_table_init': /kisskb/src/drivers/firmware/google/coreboot_table.c:102:9: warning: 'ret' 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/nvme/host/lightnvm.c: In function 'nvme_nvm_get_chk_meta': /kisskb/src/drivers/nvme/host/lightnvm.c:624:2: warning: 'ret' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/pinctrl/intel/pinctrl-cherryview.c: In function 'chv_gpio_probe': /kisskb/src/drivers/pinctrl/intel/pinctrl-cherryview.c:1647:29: warning: 'irq_base' may be used uninitialized in this function [-Wuninitialized] fs/aio.o: warning: objtool: aio_nr_sub()+0x31: unreachable instruction /kisskb/src/arch/x86/kernel/e820.c: In function 'e820__setup_pci_gap': /kisskb/src/arch/x86/kernel/e820.c:653:2: warning: 'gapstart' 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/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] drivers/clk/clk.o: warning: objtool: clk_prepare_unlock()+0x44: unreachable instruction /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] kernel/rcu/tree.o: warning: objtool: rcu_init_geometry()+0x65: unreachable instruction /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] Completed OK # rm -rf /kisskb/build/linus-rand_x86_64-randconfig_x86_64 # Build took: 0:03:50.658357