On Wed, Aug 04, 2021 at 08:43:43AM -0600, Jens Axboe wrote: > Daniel reports that the v5.14-rc4-rt4 kernel throws a BUG when running > stress-ng: > > | [ 90.202543] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:35 > | [ 90.202549] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 2047, name: iou-wrk-2041 > | [ 90.202555] CPU: 5 PID: 2047 Comm: iou-wrk-2041 Tainted: G W 5.14.0-rc4-rt4+ #89 > | [ 90.202559] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 > | [ 90.202561] Call Trace: > | [ 90.202577] dump_stack_lvl+0x34/0x44 > | [ 90.202584] ___might_sleep.cold+0x87/0x94 > | [ 90.202588] rt_spin_lock+0x19/0x70 > | [ 90.202593] ___slab_alloc+0xcb/0x7d0 > | [ 90.202598] ? newidle_balance.constprop.0+0xf5/0x3b0 > | [ 90.202603] ? dequeue_entity+0xc3/0x290 > | [ 90.202605] ? io_wqe_dec_running.isra.0+0x98/0xe0 > | [ 90.202610] ? pick_next_task_fair+0xb9/0x330 > | [ 90.202612] ? __schedule+0x670/0x1410 > | [ 90.202615] ? io_wqe_dec_running.isra.0+0x98/0xe0 > | [ 90.202618] kmem_cache_alloc_trace+0x79/0x1f0 > | [ 90.202621] io_wqe_dec_running.isra.0+0x98/0xe0 > | [ 90.202625] io_wq_worker_sleeping+0x37/0x50 > | [ 90.202628] schedule+0x30/0xd0 > | [ 90.202630] schedule_timeout+0x8f/0x1a0 > | [ 90.202634] ? __bpf_trace_tick_stop+0x10/0x10 > | [ 90.202637] io_wqe_worker+0xfd/0x320 > | [ 90.202641] ? finish_task_switch.isra.0+0xd3/0x290 > | [ 90.202644] ? io_worker_handle_work+0x670/0x670 > | [ 90.202646] ? io_worker_handle_work+0x670/0x670 > | [ 90.202649] ret_from_fork+0x22/0x30 > > which is due to the RT kernel not liking a GFP_ATOMIC allocation inside > a raw spinlock. Besides that not working on RT, doing any kind of > allocation from inside schedule() is kind of nasty and should be avoided > if at all possible. > > This particular path happens when an io-wq worker goes to sleep, and we > need a new worker to handle pending work. We currently allocate a small > data item to hold the information we need to create a new worker, but we > can instead include this data in the io_worker struct itself and just > protect it with a single bit lock. We only really need one per worker > anyway, as we will have run pending work between to sleep cycles. > > https://lore.kernel.org/lkml/20210804082418.fbibprcwtzyt5qax@xxxxxxxxxxxxx/ > Reported-by: Daniel Wagner <dwagner@xxxxxxx> > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> I applied this patch on top of v5.14-rc4-rt4 and with it all looks good. Tested-by: Daniel Wagner <dwagner@xxxxxxx>
