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
