Johannes Stezenbach <js@xxxxxxxxxxx> :
[...]
> > The driver does too much (slow) things in its softirq part. A part of it
> > should probably be posted to a workqueue. Doable but it is not a 5min hack.
>
> What exactly is too slow to do from a tasklet?
Any code which can go to sleep. For instance:
debiirq
-> dvb_dmx_swfilter_packets (spin_locks: so far, so good)
-> dvb_dmx_swfilter_packet
-> dvb_dmx_swfilter_packet_type
-> dvb_dmx_swfilter_packet_type
-> av7110_write_to_decoder
-> av7110_ipack_flush
-> send_ipack
-> play_video_cb
-> get_video_format
-> av7110_set_vidmode
-> av7110_fw_cmd
-> av7110_send_fw_cmd
!
! Issues down_interruptible: broken because of spinlock above or
! tasklet/softirq context (pick one).
!
-> __av7110_send_fw_cmd
!
! Can issue msleep like crazy: broken (same reason)
!
-> rdebi (spin_lock_irqsaves: ok)
-> av7110_debiread
-> saa7146_wait_for_debi_done
!
! It does not sleep but it busy waits up to 50 ms (presumably when hardware
! is kaputt, I can buy that but please remember that the days of matrox induced
! bus stalls are not _that_ far), 2 times. Btw I am not convinced that it is
! safe to expect jiffies to be updated when in code protected by a
! spin_lock_irqsave.
!
Don't hesitate to educate me if I am wrong but this code seems severely
broken wrt locking rules (not that it prevents to be useful/workable for
a lot of people :o) ).
--
Ueimor
