cvs commit: src/sys/net80211 ieee80211_ioctl.c

[John Baldwin]

On Thursday 03 March 2005 12:35 pm, Bill Paul wrote:
> wpaul       2005-03-03 17:35:05 UTC
>
>   FreeBSD src repository
>
>   Modified files:
>     sys/net80211         ieee80211_ioctl.c
>   Log:
>   Recently, it was reported to me that you could provoke a double fault
>   panic with the NDISulator if you did "ifconfig ndis0 10.0.0.1/24,"
>   whereas "ifconfig ndis0 10.0.0.1/24 up" worked fine. The double fault
>   was caused by the ifconfig thread running out of kernel stack space.
>   (This was partly due to the NDIsulator using a couple of big buffers on
>   the stack, but even after fixing that the double fault persisted.)
>
>   It turns out that ndis_init() is called in both cases, but in the first
>   case the code path passes through ieee80211_ioctl(), and it turns out
>   ieee80211_ioctl() consumes a whopping 2400 bytes of stack space.
>   Apparently, gcc -O2 causes the ieee80211_ioctl_get80211() routine to
>   be inlined into ieee80211_ioctl(), and for some reason which I do not
>   fully understand, this causes ieee80211_ioctl() to consume an extra 2K
>   of stack space.
>
>   To prevent this overly agressive optimization, ieee80211_ioctl_get80211()
>   is now declared with __attribute__ ((noinline)). With this change,
>   ieee80211_ioctl() now only reserves about 200 bytes of stack instead of
> 2400.

Hmm, this might fix the double fault panics with wlan_wep.ko when WITNESS is 
enabled as well.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org