tree 58414d19e2477200b3e803f166567994a79972cb
parent eb4a5527b1f0d581ac217c80ef3278ed5e38693c
author David Woodhouse <David.Woodhouse@intel.com> 1281247379 -0700
committer David S. Miller <davem@davemloft.net> 1281247379 -0700

solos-pci: Fix race condition in tasklet RX handling

We were seeing faults in the solos-pci receive tasklet when packets
arrived for a VCC which was currently being closed:

[18842.727906] EIP: [<e082f490>] br2684_push+0x19/0x234 [br2684] SS:ESP 0068:dfb89d14 

[18845.090712] [<c13ecff3>] ? do_page_fault+0x0/0x2e1 
[18845.120042] [<e082f490>] ? br2684_push+0x19/0x234 [br2684] 
[18845.153530] [<e084fa13>] solos_bh+0x28b/0x7c8 [solos_pci] 
[18845.186488] [<e084f711>] ? solos_irq+0x2d/0x51 [solos_pci] 
[18845.219960] [<c100387b>] ? handle_irq+0x3b/0x48 
[18845.247732] [<c10265cb>] ? irq_exit+0x34/0x57 
[18845.274437] [<c1025720>] tasklet_action+0x42/0x69 
[18845.303247] [<c102643f>] __do_softirq+0x8e/0x129 
[18845.331540] [<c10264ff>] do_softirq+0x25/0x2a 
[18845.358274] [<c102664c>] _local_bh_enable_ip+0x5e/0x6a 
[18845.389677] [<c102666d>] local_bh_enable+0xb/0xe 
[18845.417944] [<e08490a8>] ppp_unregister_channel+0x32/0xbb [ppp_generic] 
[18845.458193] [<e08731ad>] pppox_unbind_sock+0x18/0x1f [pppox] 

This patch uses an RCU-inspired approach to fix it. In the RX tasklet's
find_vcc() function we first refuse to use a VCC which already has the
ATM_VF_READY bit cleared. And in the VCC close function, we synchronise
with the tasklet to ensure that it can't still be using the VCC before
we continue and allow the VCC to be destroyed.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Tested-by: Nathan Williams <nathan@traverse.com.au>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>