On Thu, 13 Sep 2018, Jia-Ju Bai wrote: > hid_alloc_report_buf() has to be called with GFP_ATOMIC in > __hid_request(), because there are the following callchains > leading to __hid_request() being an atomic context: > > picolcd_send_and_wait (acquire a spinlock) > hid_hw_request > __hid_request > hid_alloc_report_buf(GFP_KERNEL) > > picolcd_reset (acquire a spinlock) > hid_hw_request > __hid_request > hid_alloc_report_buf(GFP_KERNEL) > > lg4ff_play (acquire a spinlock) > hid_hw_request > __hid_request > hid_alloc_report_buf(GFP_KERNEL) > > lg4ff_set_autocenter_ffex (acquire a spinlock) > hid_hw_request > __hid_request > hid_alloc_report_buf(GFP_KERNEL) Hm, so it's always drivers calling out into core in atomic context. So either we take this, and put our bets on being able to allocate the buffer without sleeping, or actually fix the few drivers (it's just lg4ff and picolcd at the end of the day) not to do that, and explicitly anotate __hid_request() with might_sleep(). Hmm? Thanks, -- Jiri Kosina SUSE Labs
