Messages in this thread | | | Subject | Re: [PATCH V2] hid: hid-core: Fix a sleep-in-atomic-context bug in __hid_request() | From | Jia-Ju Bai <> | Date | Thu, 4 Oct 2018 11:14:52 +0800 |
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On 2018/9/30 3:20, Jiri Kosina wrote: > On Sat, 29 Sep 2018, Jia-Ju Bai wrote: > >>>> 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, >> In my opinion, I prefer this way. > Why? Forcing all the report buffer to be limited to be non-sleeping > allocations just because of two drivers, looks like an overkill, and > actually calls for more issues (as GFP_ATOMIC is of course in principle > less likely to succeed). >
Okay, I thought that using GFP_ATOMIC is the simplest way to fix these bugs. But I check the Linux kernel code again, and find that hid_hw_request() are called at many places. So changing this function may affect many drivers. I agree to only change the two drivers, and explicitly anotate __hid_request() with might_sleep().
Best wishes, Jia-Ju Bai
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