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  1. 21 6月, 2007 4 次提交
    • L
      spidernet: silence the ramfull messages · c3d1182a
      由 Linas Vepstas 提交于 
      Although the previous patch resolved issues with hangs when the
RX ram full interrupt is encountered, there are still situations
where lots of RX ramfull interrupts arrive, resulting in a noisy
log in syslog. There is no need for this.
Signed-off-by: NLinas Vepstas <linas@austin.ibm.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>
      c3d1182a
    • L
      spidernet: Don't terminate the RX ring · 2bf27a0d
      由 Linas Vepstas 提交于 
      The terminated RX ring will cause trouble during the RX ram full
conditions, leading to a hung driver, as the hardware can't find
the next descr.  There is no real reason to terminate the RX ring;
it doesn't make the operation any smooother, and it does
require an extra sync. So don't do it.
Signed-off-by: NLinas Vepstas <linas@austin.ibm.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>
      2bf27a0d
    • L
      spidernet: Cure RX ram full bug · 4c4bd5a9
      由 Linas Vepstas 提交于 
      This patch fixes a rare deadlock that can occur when the kernel
is not able to empty out the RX ring quickly enough. Below follows
a detailed description of the bug and the fix.

As long as the OS can empty out the RX buffers at a rate faster than
the hardware can fill them, there is no problem. If, for some reason,
the OS fails to empty the RX ring fast enough, the hardware GDACTDPA
pointer will catch up to the head, notice the not-empty condition,
ad stop. However, RX packets may still continue arriving on the wire.
The spidernet chip can save some limited number of these in local RAM.
When this local ram fills up, the spider chip will issue an interrupt
indicating this (GHIINT0STS will show ERRINT, and the GRMFLLINT bit
will be set in GHIINT1STS).  When te RX ram full condition occurs,
a certain bug/feature is triggered that has to be specially handled.
This section describes the special handling for this condition.

When the OS finally has a chance to run, it will empty out the RX ring.
In particular, it will clear the descriptor on which the hardware had
stopped. However, once the hardware has decided that a certain
descriptor is invalid, it will not restart at that descriptor; instead
it will restart at the next descr. This potentially will lead to a
deadlock condition, as the tail pointer will be pointing at this descr,
which, from the OS point of view, is empty; the OS will be waiting for
this descr to be filled. However, the hardware has skipped this descr,
and is filling the next descrs. Since the OS doesn't see this, there
is a potential deadlock, with the OS waiting for one descr to fill,
while the hardware is waiting for a differen set of descrs to become
empty.

A call to show_rx_chain() at this point indicates the nature of the
problem. A typical print when the network is hung shows the following:

net eth1: Spider RX RAM full, incoming packets might be discarded!
net eth1: Total number of descrs=256
net eth1: Chain tail located at descr=255
net eth1: Chain head is at 255
net eth1: HW curr desc (GDACTDPA) is at 0
net eth1: Have 1 descrs with stat=xa0800000
net eth1: HW next desc (GDACNEXTDA) is at 1
net eth1: Have 127 descrs with stat=x40800101
net eth1: Have 1 descrs with stat=x40800001
net eth1: Have 126 descrs with stat=x40800101
net eth1: Last 1 descrs with stat=xa0800000

Both the tail and head pointers are pointing at descr 255, which is
marked xa... which is "empty". Thus, from the OS point of view, there
is nothing to be done. In particular, there is the implicit assumption
that everything in front of the "empty" descr must surely also be empty,
as explained in the last section. The OS is waiting for descr 255 to
become non-empty, which, in this case, will never happen.

The HW pointer is at descr 0. This descr is marked 0x4.. or "full".
Since its already full, the hardware can do nothing more, and thus has
halted processing. Notice that descrs 0 through 254 are all marked
"full", while descr 254 and 255 are empty. (The "Last 1 descrs" is
descr 254, since tail was at 255.) Thus, the system is deadlocked,
and there can be no forward progress; the OS thinks there's nothing
to do, and the hardware has nowhere to put incoming data.

This bug/feature is worked around with the spider_net_resync_head_ptr()
routine. When the driver receives RX interrupts, but an examination
of the RX chain seems to show it is empty, then it is probable that
the hardware has skipped a descr or two (sometimes dozens under heavy
network conditions). The spider_net_resync_head_ptr() subroutine will
search the ring for the next full descr, and the driver will resume
operations there.  Since this will leave "holes" in the ring, there
is also a spider_net_resync_tail_ptr() that will skip over such holes.
Signed-off-by: NLinas Vepstas <linas@austin.ibm.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>
      4c4bd5a9
    • L
      spidernet: null out skb pointer after its been used. · 83d35145
      由 Linas Vepstas 提交于 
      Avoid kernel crash in mm/slab.c due to double-free of pointer.

If the ethernet interface is brought down while there is still
RX traffic in flight, the device shutdown routine can end up
trying to double-free an skb, leading to a crash in mm/slab.c
Avoid the double-free by nulling out the skb pointer.
Signed-off-by: NLinas Vepstas <linas@austin.ibm.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>
      83d35145
  3. 03 6月, 2007 1 次提交
  5. 25 5月, 2007 1 次提交
  7. 18 5月, 2007 1 次提交
  9. 12 5月, 2007 1 次提交
  11. 02 5月, 2007 1 次提交
  13. 26 4月, 2007 3 次提交
  15. 20 4月, 2007 1 次提交
    • L
      spidernet: Fix problem sending IP fragments · 33bdeec8
      由 Linas Vepstas 提交于 
      The basic structure of "normal" UDP/IP/Ethernet
frames (that actually work):
 - It starts with the Ethernet header (dest MAC, src MAC, etc.)
 - The next part is occupied by the IP header (version info, length of
packet, id=0, fragment offset=0, checksum, from / to address, etc.)
 - Then comes the UDP header (src / dest port, length, checksum)
 - Actual payload
 - Ethernet checksum

Now what's different for IP fragment:
 - The IP header has id set to some value (same for all fragments),
offset is set appropriately (i.e. 0 for first fragment, following
according to size of other fragments), size is the length of the frame.
 - UDP header is unchanged. I.e. length is according to full UDP
datagram, not just the part within the actual frame! But this is only
true within the first frame: all following frames don't have a valid
UDP-header at all.

The spidernet silicon seems to be quite intelligent: It's able to
compute (IP / UDP / Ethernet) checksums on the fly and tests if frames
are conforming to RFC -- at least conforming to RFC on complete frames.

But IP fragments are different as explained above:
I.e. for IP fragments containing part of a UDP datagram it sees
incompatible length in the headers for IP and UDP in the first frame
and, thus, skips this frame. But the content *is* correct for IP
fragments. For all following frames it finds (most probably) no valid
UDP header at all. But this *is* also correct for IP fragments.

The Linux IP-stack seems to be clever in this point. It expects the
spidernet to calculate the checksum (since the module claims to be able
to do so) and marks the skb's for "normal" frames accordingly
(ip_summed set to CHECKSUM_HW).
But for the IP fragments it does not expect the driver to be capable to
handle the frames appropriately. Thus all checksums are allready
computed. This is also flaged within the skb (ip_summed set to
CHECKSUM_NONE).

Unfortunately the spidernet driver ignores that hints. It tries to send
the IP fragments of UDP datagrams as normal UDP/IP frames. Since they
have different structure the silicon detects them the be not
"well-formed" and skips them.

The following one-liner against 2.6.21-rc2 changes this behavior. If the
IP-stack claims to have done the checksumming, the driver should not
try to checksum (and analyze) the frame but send it as is.
Signed-off-by: NNorbert Eicker <n.eicker@fz-juelich.de>
Signed-off-by: NLinas Vepstas <linas@austin.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>
      33bdeec8
  17. 13 4月, 2007 1 次提交
  19. 27 2月, 2007 10 次提交
  21. 10 2月, 2007 1 次提交
  23. 08 2月, 2007 1 次提交
  25. 06 2月, 2007 13 次提交
  27. 02 2月, 2007 1 次提交