Tejun Heo 23d11a58a9 workqueue: skip flush dependency checks for legacy workqueues ... fca839c00a ("workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue") implemented flush dependency warning which triggers if a PF_MEMALLOC task or WQ_MEM_RECLAIM workqueue tries to flush a !WQ_MEM_RECLAIM workquee. This assumes that workqueues marked with WQ_MEM_RECLAIM sit in memory reclaim path and making it depend on something which may need more memory to make forward progress can lead to deadlocks. Unfortunately, workqueues created with the legacy create*_workqueue() interface always have WQ_MEM_RECLAIM regardless of whether they are depended upon memory reclaim or not. These spurious WQ_MEM_RECLAIM markings cause spurious triggering of the flush dependency checks. WARNING: CPU: 0 PID: 6 at kernel/workqueue.c:2361 check_flush_dependency+0x138/0x144() workqueue: WQ_MEM_RECLAIM deferwq:deferred_probe_work_func is flushing !WQ_MEM_RECLAIM events:lru_add_drain_per_cpu ... Workqueue: deferwq deferred_probe_work_func [<c0017acc>] (unwind_backtrace) from [<c0013134>] (show_stack+0x10/0x14) [<c0013134>] (show_stack) from [<c0245f18>] (dump_stack+0x94/0xd4) [<c0245f18>] (dump_stack) from [<c0026f9c>] (warn_slowpath_common+0x80/0xb0) [<c0026f9c>] (warn_slowpath_common) from [<c0026ffc>] (warn_slowpath_fmt+0x30/0x40) [<c0026ffc>] (warn_slowpath_fmt) from [<c00390b8>] (check_flush_dependency+0x138/0x144) [<c00390b8>] (check_flush_dependency) from [<c0039ca0>] (flush_work+0x50/0x15c) [<c0039ca0>] (flush_work) from [<c00c51b0>] (lru_add_drain_all+0x130/0x180) [<c00c51b0>] (lru_add_drain_all) from [<c00f728c>] (migrate_prep+0x8/0x10) [<c00f728c>] (migrate_prep) from [<c00bfbc4>] (alloc_contig_range+0xd8/0x338) [<c00bfbc4>] (alloc_contig_range) from [<c00f8f18>] (cma_alloc+0xe0/0x1ac) [<c00f8f18>] (cma_alloc) from [<c001cac4>] (__alloc_from_contiguous+0x38/0xd8) [<c001cac4>] (__alloc_from_contiguous) from [<c001ceb4>] (__dma_alloc+0x240/0x278) [<c001ceb4>] (__dma_alloc) from [<c001cf78>] (arm_dma_alloc+0x54/0x5c) [<c001cf78>] (arm_dma_alloc) from [<c0355ea4>] (dmam_alloc_coherent+0xc0/0xec) [<c0355ea4>] (dmam_alloc_coherent) from [<c039cc4c>] (ahci_port_start+0x150/0x1dc) [<c039cc4c>] (ahci_port_start) from [<c0384734>] (ata_host_start.part.3+0xc8/0x1c8) [<c0384734>] (ata_host_start.part.3) from [<c03898dc>] (ata_host_activate+0x50/0x148) [<c03898dc>] (ata_host_activate) from [<c039d558>] (ahci_host_activate+0x44/0x114) [<c039d558>] (ahci_host_activate) from [<c039f05c>] (ahci_platform_init_host+0x1d8/0x3c8) [<c039f05c>] (ahci_platform_init_host) from [<c039e6bc>] (tegra_ahci_probe+0x448/0x4e8) [<c039e6bc>] (tegra_ahci_probe) from [<c0347058>] (platform_drv_probe+0x50/0xac) [<c0347058>] (platform_drv_probe) from [<c03458cc>] (driver_probe_device+0x214/0x2c0) [<c03458cc>] (driver_probe_device) from [<c0343cc0>] (bus_for_each_drv+0x60/0x94) [<c0343cc0>] (bus_for_each_drv) from [<c03455d8>] (__device_attach+0xb0/0x114) [<c03455d8>] (__device_attach) from [<c0344ab8>] (bus_probe_device+0x84/0x8c) [<c0344ab8>] (bus_probe_device) from [<c0344f48>] (deferred_probe_work_func+0x68/0x98) [<c0344f48>] (deferred_probe_work_func) from [<c003b738>] (process_one_work+0x120/0x3f8) [<c003b738>] (process_one_work) from [<c003ba48>] (worker_thread+0x38/0x55c) [<c003ba48>] (worker_thread) from [<c0040f14>] (kthread+0xdc/0xf4) [<c0040f14>] (kthread) from [<c000f778>] (ret_from_fork+0x14/0x3c) Fix it by marking workqueues created via create*_workqueue() with __WQ_LEGACY and disabling flush dependency checks on them. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-tested-by: Thierry Reding <thierry.reding@gmail.com> Link: http://lkml.kernel.org/g/20160126173843.GA11115@ulmo.nvidia.com Fixes: fca839c00a ("workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue")		2016-01-29 13:31:10 -05:00
..
acpi	Merge branches 'acpica', 'acpi-video' and 'acpi-fan'	2016-01-21 00:41:59 +01:00
asm-generic	Merge branch 'akpm' (patches from Andrew)	2016-01-21 12:32:08 -08:00
clocksource
crypto	Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6	2016-01-22 11:58:43 -08:00
drm	Merge tag 'topic/drm-misc-2016-01-17' of git://anongit.freedesktop.org/drm-intel into drm-next	2016-01-18 07:01:16 +10:00
dt-bindings	ARM: SoC driver updates for v4.5	2016-01-20 18:42:30 -08:00
keys
kvm
linux	workqueue: skip flush dependency checks for legacy workqueues	2016-01-29 13:31:10 -05:00
math-emu
media	[media] media-entitiy: add a function to create multiple links	2016-01-11 12:19:26 -02:00
memory
misc
net	net: drop tcp_memcontrol.c	2016-01-20 17:09:18 -08:00
pcmcia
ras
rdma	IB/mlx4: Enable send of RoCE QP1 packets with IP/UDP headers	2016-01-19 15:35:01 -05:00
rxrpc
scsi	Initial roundup of 4.5 merge window patches	2016-01-23 18:45:06 -08:00
soc	ARM: SoC driver updates for v4.5	2016-01-20 18:42:30 -08:00
sound	ALSA: timer: Introduce disconnect op to snd_timer_instance	2016-01-21 17:51:42 +01:00
target	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending	2016-01-20 17:20:53 -08:00
trace	Initial roundup of 4.5 merge window patches	2016-01-23 18:45:06 -08:00
uapi	Some locking and page fault bug fixes from Jan Kara, some ext4	2016-01-22 11:23:35 -08:00
video
xen	Merge branch 'for-4.5/drivers' of git://git.kernel.dk/linux-block	2016-01-21 18:19:38 -08:00
Kbuild