Re: 2.5 kernel + hostap_cs + X11 = scheduling while atomic

[Jouni Malinen <jkmaline@cc.hut.fi>]

On Tue, Feb 04, 2003 at 11:36:37PM -0800, Joshua Kwan wrote:

> However, a combination of running said kernel, hostap_cs, and X11 produces
> this nasty infinite string of errors:
> 
> bad: scheduling while atomic!
> Call Trace:

>  [<d2948a30>] hfa384x_get_rid+0x36/0x2d6b7606 [hostap_cs]

That will sleep, so it better not be called while in interrupt context
or apparently also, while atomic with preemptive kernels(?).

>  [<d29388b5>] hostap_get_wireless_stats+0xa6/0x2d6c77f1 [hostap]

That's the dev->get_wireless_stats handler. I have assumed that it is
allowed to sleep there, but apparently that is not the case with Linux
2.5.x (at least with CONFIG_PREEMPT). I added a workaround for this into
Host AP CVS, but you will not get signal quality statistics in that
case. I'll do a proper fix if that function is indeed not allowed to
sleep (e.g., by collecting the statistics before and just copying the
values here).

Jean, do you have a comment on this? This happens, e.g., when executing
'cat /proc/net/wireless':

>  [<c0168f45>] seq_printf+0x45/0x56
>  [<c02bd9b6>] wireless_seq_show+0xd6/0xf7
>  [<c0141dd5>] do_mmap_pgoff+0x40e/0x6dc
>  [<c0168a56>] seq_read+0x1c9/0x2ee
>  [<c014d20f>] vfs_read+0xbc/0x127
>  [<c014d496>] sys_read+0x3e/0x55
>  [<c01093cb>] syscall_call+0x7/0xb

-- 
Jouni Malinen                                            PGP id EFC895FA