Default HW configuration is optimal for an architecture where cache
line size is 64B.
During chip initialization, properly initialize the cache line size
in HW to avoid possible redundant PCI transactions.
Signed-off-by: Tomer Tayar <Tomer.Tayar@cavium.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
In order to access HW registers driver needs to acquire a PTT entry
[mapping between bar memory and internal chip address].
Since acquiring PTT entries could fail [at least in theory] as their
number is finite and other flows can hold them, we reserve special PTT
entries for 'important' enough flows - ones we want to guarantee that
would not be susceptible to such issues.
One such special entry is the 'main' PTT which is meant to be used in
flows such as chip initialization and de-initialization.
However, there are other flows that are also using that same entry
for their own purpose, and might run concurrently with the original
flows [notice that for most cases using the main-ptt by mistake, such
a race is still impossible, at least today].
This patch re-organizes the various functions that currently use the
main_ptt in one of two ways:
- If a function shouldn't use the main_ptt it starts acquiring and
releasing it's own PTT entry and use it instead. Notice if those
functions previously couldn't fail, they now can [as acquisition
might fail].
- Change the prototypes so that the main_ptt would be received as
a parameter [instead of explicitly accessing it].
This prevents the future risk of adding codes that introduces new
use-cases for flows using the main_ptt, ones that might be in race
with the actual 'main' flows.
Signed-off-by: Rahul Verma <Rahul.Verma@cavium.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
PTT entries are per-hwfn; If some errneous flow is trying
to use a PTT belonging to a differnet hwfn warn user, as this
can break every register accessing flow later and is very hard
to root-cause.
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Merge tag 'rxrpc-rewrite-20170406' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
David Howells says:
====================
rxrpc: Miscellany
Here's a set of patches that make some minor changes to AF_RXRPC:
(1) Store error codes in struct rxrpc_call::error as negative codes and
only convert to positive in recvmsg() to avoid confusion inside the
kernel.
(2) Note the result of trying to abort a call (this fails if the call is
already 'completed').
(3) Don't abort on temporary errors whilst processing challenge and
response packets, but rather drop the packet and wait for
retransmission.
And also adds some more tracing:
(4) Protocol errors.
(5) Received abort packets.
(6) Changes in the Rx window size due to ACK packet information.
(7) Client call initiation (to allow the rxrpc_call struct pointer, the
wire call ID and the user ID/afs_call pointer to be cross-referenced).
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Jeff Kirsher says:
====================
100GbE Intel Wired LAN Driver Updates 2017-04-05
This series contains updates to fm10k only.
Phil Turnbull from Oracle fixes an issue where the argument provided to
FM10K_REMOVED macro was not what was expecting.
Jake modifies the driver to replace the bitwise operators and defines with
a BITMAP and enumeration values to avoid race conditions. Also future
proof the driver so that developers do not have to remember to re-size the
bitmaps when adding new values. Fixed the wording of a code comment to
avoid stating that we return a value for a void function.
Ngai-Mint makes sure that when configuring the receive ring, we make sure
the receive queue is disabled. Fixed an issue where interfaces were
resetting because the transmit mailbox FIFO was becoming full since the
host was not ready, so ensure the host is ready before queueing up
mailbox messages.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
R. Parameswaran says:
====================
L2TP:Adjust intf MTU, add underlay L3, L2 hdrs.
Existing L2TP kernel code does not derive the optimal MTU for Ethernet
pseudowires and instead leaves this to a userspace L2TP daemon or
operator. If an MTU is not specified, the existing kernel code chooses
an MTU that does not take account of all tunnel header overheads, which
can lead to unwanted IP fragmentation. When L2TP is used without a
control plane (userspace daemon), we would prefer that the kernel does a
better job of choosing a default pseudowire MTU, taking account of all
tunnel header overheads, including IP header options, if any. This patch
addresses this.
Change-set is organized as a two part patch series, with one patch
introducing a new kernel function to compute the IP overhead on a
socket, and the other patch using this new kernel function to compute
the default L2TP MTU for an Ethernet pseudowire.
Existing code also seems to assume an Ethernet (non-jumbo) underlay. The
change proposed here uses the PMTU mechanism and the dst entry in the
L2TP tunnel socket to directly pull up the underlay MTU (as the baseline
number on top of which the encapsulation headers are factored in).
An default MTU value of 1500 bytes is assumed as a fallback only if
this fails.
Fixed the kbuild test robot error in the previous posting.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Existing L2TP kernel code does not derive the optimal MTU for Ethernet
pseudowires and instead leaves this to a userspace L2TP daemon or
operator. If an MTU is not specified, the existing kernel code chooses
an MTU that does not take account of all tunnel header overheads, which
can lead to unwanted IP fragmentation. When L2TP is used without a
control plane (userspace daemon), we would prefer that the kernel does a
better job of choosing a default pseudowire MTU, taking account of all
tunnel header overheads, including IP header options, if any. This patch
addresses this.
Change-set here uses the new kernel function, kernel_sock_ip_overhead(),
to factor the outer IP overhead on the L2TP tunnel socket (including
IP Options, if any) when calculating the default MTU for an Ethernet
pseudowire, along with consideration of the inner Ethernet header.
Signed-off-by: R. Parameswaran <rparames@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
A new function, kernel_sock_ip_overhead(), is provided
to calculate the cumulative overhead imposed by the IP
Header and IP options, if any, on a socket's payload.
The new function returns an overhead of zero for sockets
that do not belong to the IPv4 or IPv6 address families.
This is used in the L2TP code path to compute the
total outer IP overhead on the L2TP tunnel socket when
calculating the default MTU for Ethernet pseudowires.
Signed-off-by: R. Parameswaran <rparames@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
While unlikely, this makes sure any format strings in the device name
can't exposure information via the resulting workqueue name.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
While unlikely, this makes sure the workqueue name won't be processed
as a format string.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
When qedr is enabled, qed would try dividing the msi-x vectors between
L2 and RoCE, starting with L2 and providing it with sufficient vectors
for its queues.
Problem is qed would also do that for storage partitions, and as those
don't need queues it would lead qed to award those partitions with 0
msi-x vectors, causing them to believe theye're using INTa and
preventing them from operating.
Fixes: 51ff17251c ("qed: Add support for RoCE hw init")
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Florian Fainelli says:
====================
net: dsa: Mock-up driver couple fixes
Thanks to Dan's static checker, a bunch of small issues were found in the code.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Dan's static checker reported the following:
drivers/net/dsa/dsa_loop.c:223 dsa_loop_port_vlan_dump()
error: uninitialized symbol 'err'.
which could happen if we do hit the continue statement for each iteration of
the loop. Initialize err to 0 here.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 98cd1552ea ("net: dsa: Mock-up driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Dan's static analyzer reported the following:
drivers/net/dsa/dsa_loop.c:181 dsa_loop_port_vlan_del()
error: XXX uninitialized symbol 'pvid'.
we were missing the assignment of pvid to ps->vid, so add that.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 98cd1552ea ("net: dsa: Mock-up driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit c7e2b9689e "sched: introduce vlan action" added both the
UAPI values for the vlan actions (TCA_VLAN_ACT_) and these two
in-kernel ones which are not used, remove them.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
mlx4 is the only driver in the tree making a point to recompute
shinfo->gso_segs.
Lets remove superfluous code.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There seems to be a missing break on the OOO_LB_TC case, pq_id
is being assigned and then re-assigned on the fall through default
case and that seems suspect.
Detected by CoverityScan, CID#1424402 ("Missing break in switch")
Fixes: b5a9ee7cf3 ("qed: Revise QM cofiguration")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit 9008ae0748 ("net/mlx5e: Minimize mlx5e_{open/close}_locked")
copied the calls to netif_set_real_num_{tx,rx}_queues from
mlx5e_open_locked to mlx5e_activate_priv_channels and wraps them in an
if condition to test for netdev->real_num_{tx,rx}_queues.
But netdev->real_num_rx_queues is conditionally compiled in if CONFIG_SYSFS
is set. Without CONFIG_SYSFS the build fails:
drivers/net/ethernet/mellanox/mlx5/core/en_main.c: In function 'mlx5e_activate_priv_channels':
drivers/net/ethernet/mellanox/mlx5/core/en_main.c:2515:12: error: 'struct net_device' has no member named 'real_num_rx_queues'; did you mean 'real_num_tx_queues'?
Fix this by unconditionally call netif_set_real_num{tx,rx}_queues like before
commit 9008ae0748.
Fixes: 9008ae0748 ("net/mlx5e: Minimize mlx5e_{open/close}_locked")
Signed-off-by: Tobias Regnery <tobias.regnery@gmail.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Prepare to mark sensitive kernel structures for randomization by making
sure they're using designated initializers. These were identified during
allyesconfig builds of x86, arm, and arm64, and the initializer fixes
were extracted from grsecurity. In this case, NULL initialize with { }
instead of undesignated NULLs.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Benjamin Herrenschmidt says:
====================
ftgmac100: Rework batch 1 - Link & Interrupts
This is version 2 of the first batch of updates to the
ftgmac100 driver.
Essentially:
- A few misc cleanups
- Fixing link speed & duplex handling (including dealing with
an Aspeed requirement to double reset the controller when
the speed changes)
- And addition of a reset task workqueue which will be used
for delaying the re-initialization of the controller
- Fixing a number of issues with how interrupts and NAPI
are dealt with.
Subsequent batches will rework and improve the rx path, the
tx path, and add a bunch of features and fixes.
Version 2 addresses some review comments to patches 5 and 10
(see version history in the respective emails).
====================
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
First, don't look at the interrupt status in the poll loop
to decide what to poll. It's wrong. If we have run out of
budget, we may still have RX packets to unqueue but no more
RX interrupt pending.
So instead move the code looking at the interrupt status
into the interrupt handler where it belongs. That avoids a slow
MMIO read in the NAPI fast path. We keep the abnormal interrupts
enabled while NAPI is scheduled.
While at it, actually do something useful in the "error" cases:
On AHB bus error, trigger the new reset task, that's about all
we can do. On RX packet fifo or descriptor overflows, we need
to restart the MAC after having freed things up. So set a flag
that NAPI will see and use to perform that restart after
harvesting the RX ring.
Finally, we shouldn't complete NAPI if there are still outgoing
packets that will need harvesting. Waiting for more interrupts
is less efficient than letting NAPI run a while longer while
the queue drains.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The interrupt is neither enabled nor registered when the interface
isn't running (regardless of whether we use nc-si or not) so the
test isn't useful.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The HW requires a full MAC reset when changing the speed.
Additionally the Aspeed documentation spells out that the
MAC needs to be reset twice with a 10us interval.
We thus move the speed setting and top level reset code
into a new ftgmac100_reset_and_config_mac() function which
handles both. Move the ring pointers initialization there
too in order to reflect the HW change.
Also reduce the timeout for the MAC reset as it shouldn't
take more than 300 clock cycles according to the doc.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Link speed changes require a full HW reset. This isn't done
properly at the moment. It will involve delays and thus isn't
suitable to do from the link poll callback.
So let's create a reset_task that we can queue up when the
link changes. It will be useful for various cases of error
handling as well.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
The link monitoring and error handling code will have to
redo the ring inits and HW setup so move the code out of
ftgmac100_open() into a dedicated function.
This forces a bit of re-ordering of ftgmac100_open() but
nothing dramatic.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The interrupt isn't shared, so this will keep it masked
until we have the HW in a known sane state.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently, a single function is used to allocate the rings
themselves, initialize them, populate the rx ring, and
allocate the rx buffers. The same happens on free.
This splits them into separate functions. This will be
useful when properly implementing re-initialization on
link changes and error handling when the rings will be
repopulated but not freed.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Keep track of both the current speed and duplex settings
instead of only speed and properly apply the duplex setting
to the HW.
This reworks the adjust_link() function to also avoid trying
to reconfigure the HW when there is no link and to display
the link state to the user.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
It's not used in any meaningful way
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Reorder the fields in struct ftgmac in slightly more logical
groups. Will make more sense as I add/remove some.
No code change.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The divisions they represent are not particularily meaningful
and things are going to be moving around with upcoming changes
making these comments more a burden than anything else.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
There's a placeholder already for the irq, use it
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Detection of watchdog timeout of Octeon cores is flawed and susceptible to
false alarms. Refactor by removing the detection code, and in its place,
leverage existing code that monitors for an indication from the NIC
firmware that an Octeon core crashed; expand the meaning of the indication
to "an Octeon core crashed or its watchdog timer expired". Detection of
watchdog timeout is now delegated to an exception handler in the NIC
firmware; this is free of false alarms.
Also if there's an Octeon core crash or watchdog timeout:
(1) Disable VF Ethernet links.
(2) Decrement the module refcount by an amount equal to the number of
active VFs of the NIC whose Octeon core crashed or had a watchdog
timeout. The refcount will continue to reflect the active VFs of
other liquidio NIC(s) (if present) whose Octeon cores are faultless.
Item (2) is needed to avoid the case of not being able to unload the driver
because the module refcount is stuck at some non-zero number. There is
code that, in normal cases, decrements the refcount upon receiving a
message from the firmware that a VF driver was unloaded. But in
exceptional cases like an Octeon core crash or watchdog timeout, arrival of
that particular message from the firmware might be unreliable. That normal
case code is changed to not touch the refcount in the exceptional case to
avoid contention (over the refcount) with the liquidio_watchdog kernel
thread who will carry out item (2).
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: Derek Chickles <derek.chickles@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
With GCC 6.3, we can get the following warning:
drivers/net/usb/usbnet.c:85:19: warning: 'driver_name' defined but not
used [-Wunused-const-variable=]
static const char driver_name [] = "usbnet";
^~~~~~~~~~~
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
fix artifact of merge resolution
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Mostly simple cases of overlapping changes (adding code nearby,
a function whose name changes, for example).
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a tracepoint (rxrpc_connect_call) to log the combination of rxrpc_call
pointer, afs_call pointer/user data and wire call parameters to make it
easier to match the tracebuffer contents to captured network packets.
Signed-off-by: David Howells <dhowells@redhat.com>
Add a tracepoint (rxrpc_rx_rwind_change) to log changes in a call's receive
window size as imposed by the peer through an ACK packet.
Signed-off-by: David Howells <dhowells@redhat.com>
Add a tracepoint (rxrpc_rx_proto) to record protocol errors in received
packets. The following changes are made:
(1) Add a function, __rxrpc_abort_eproto(), to note a protocol error on a
call and mark the call aborted. This is wrapped by
rxrpc_abort_eproto() that makes the why string usable in trace.
(2) Add trace_rxrpc_rx_proto() or rxrpc_abort_eproto() to protocol error
generation points, replacing rxrpc_abort_call() with the latter.
(3) Only send an abort packet in rxkad_verify_packet*() if we actually
managed to abort the call.
Note that a trace event is also emitted if a kernel user (e.g. afs) tries
to send data through a call when it's not in the transmission phase, though
it's not technically a receive event.
Signed-off-by: David Howells <dhowells@redhat.com>
In the rxkad security module, when we encounter a temporary error (such as
ENOMEM) from which we could conceivably recover, don't abort the
connection, but rather permit retransmission of the relevant packets to
induce a retry.
Note that I'm leaving some places that could be merged together to insert
tracing in the next patch.
Signed-off-by; David Howells <dhowells@redhat.com>
Make rxrpc_kernel_abort_call() return an indication as to whether it
actually aborted the operation or not so that kafs can trace the failure of
the operation. Note that 'success' in this context means changing the
state of the call, not necessarily successfully transmitting an ABORT
packet.
Signed-off-by: David Howells <dhowells@redhat.com>
Use negative error codes in struct rxrpc_call::error because that's what
the kernel normally deals with and to make the code consistent. We only
turn them positive when transcribing into a cmsg for userspace recvmsg.
Signed-off-by: David Howells <dhowells@redhat.com>
Interfaces will reset whenever the TX mailbox FIFO has become full. This
occurs more frequently whenever the IES API application is not running
to process and clear the messages in the FIFO. Thus, this could lead to
situations where the interface would enter an infinite reset loop. That
is: if the interface is trying to synchronize a huge number of unicast
and multicast entries with the IES API application, the TX mailbox FIFO
will become full and the interface resets. Once the interface exits
reset, it'll try to synchronize the unicast and multicast entries again.
Ergo, this creates an infinite loop. Other actions such as multiple
mulitcast mode or up/down transitions will fill the TX mailbox FIFO and
induce the interface to reset. To correct these situations, check if the
interface's "host_ready" flag is enabled before enqueuing any messages
to the TX mailbox FIFO. This check will be conducted by a function call.
Lastly, this issue mainly affects the PF and, thus, the VF is exempt.
Signed-off-by: Ngai-Mint Kwan <ngai-mint.kwan@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Write to RXQCTL register to disable the receive queue when configuring
the RX ring.
Signed-off-by: Ngai-Mint Kwan <ngai-mint.kwan@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Re-word the comment to avoid stating that we return a value for this
void function. Additionally, there is no need to mention older kernels,
since this is the upstream kernel.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
If some code path executes fm10k_service_event_schedule(), it is
guaranteed that we only queue the service task once, since we use
__FM10K_SERVICE_SCHED flag. Unfortunately this has a side effect that if
a service request occurs while we are currently running the watchdog, it
is possible that we will fail to notice the request and ignore it until
the next time the request occurs.
This can cause problems with pf/vf mailbox communication and other
service event tasks. To avoid this, introduce a FM10K_SERVICE_REQUEST
bit. When we successfully schedule (and set the _SCHED bit) the service
task, we will clear this bit. However, if we are unable to currently
schedule the service event, we just set the new SERVICE_REQUEST bit.
Finally, after the service event completes, we will re-schedule if the
request bit has been set.
This should ensure that we do not miss any service event schedules,
since we will re-schedule it once the currently running task finishes.
This means that for each request, we will always schedule the service
task to run at least once in full after the request came in.
This will avoid timing issues that can occur with the service event
scheduling. We do pay a cost in re-running many tasks, but all the
service event tasks use either flags to avoid duplicate work, or are
tolerant of being run multiple times.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This ensures that future programmers do not have to remember to re-size
the bitmaps due to adding new values. Although this is unlikely for this
driver, it may happen and it's best to prevent it from ever being an
issue.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Replace bitwise operators and #defines with a BITMAP and enumeration
values. This is similar to how we handle the "state" values as well.
This has two distinct advantages over the old method. First, we ensure
correctness of operations which are currently problematic due to race
conditions. Suppose that two kernel threads are running, such as the
watchdog and an ethtool ioctl, and both modify flags. We'll say that the
watchdog is CPU A, and the ethtool ioctl is CPU B.
CPU A sets FLAG_1, which can be seen as
CPU A read FLAGS
CPU A write FLAGS | FLAG_1
CPU B sets FLAG_2, which can be seen as
CPU B read FLAGS
CPU A write FLAGS | FLAG_2
However, "|=" and "&=" operators are not actually atomic. So this could
be ordered like the following:
CPU A read FLAGS -> variable
CPU B read FLAGS -> variable
CPU A write FLAGS (variable | FLAG_1)
CPU B write FLAGS (variable | FLAG_2)
Notice how the 2nd write from CPU B could actually undo the write from
CPU A because it isn't guaranteed that the |= operation is atomic.
In practice the race windows for most flag writes is incredibly narrow
so it is not easy to isolate issues. However, the more flags we have,
the more likely they will cause problems. Additionally, if such
a problem were to arise, it would be incredibly difficult to track down.
Second, there is an additional advantage beyond code correctness. We can
now automatically size the BITMAP if more flags were added, so that we
do not need to remember that flags is u32 and thus if we added too many
flags we would over-run the variable. This is not a likely occurrence
for fm10k driver, but this patch can serve as an example for other
drivers which have many more flags.
This particular change does have a bit of trouble converting some of the
idioms previously used with the #defines for flags. Specifically, when
converting FM10K_FLAG_RSS_FIELD_IPV[46]_UDP flags. This whole operation
was actually quite problematic, because we actually stored flags
separately. This could more easily show the problem of the above
re-ordering issue.
This is really difficult to test whether atomics make a difference in
practical scenarios, but you can ensure that basic functionality remains
the same. This patch has a lot of code coverage, but most of it is
relatively simple.
While we are modifying these files, update their copyright year.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
