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Ido Schimmel 759635760a mlxsw: pci: Recycle received packet upon allocation failure
When the driver fails to allocate a new Rx buffer, it passes an empty Rx
descriptor (contains zero address and size) to the device and marks it
as invalid by setting the skb pointer in the descriptor's metadata to
NULL.

After processing enough Rx descriptors, the driver will try to process
the invalid descriptor, but will return immediately seeing that the skb
pointer is NULL. Since the driver no longer passes new Rx descriptors to
the device, the Rx queue will eventually become full and the device will
start to drop packets.

Fix this by recycling the received packet if allocation of the new
packet failed. This means that allocation is no longer performed at the
end of the Rx routine, but at the start, before tearing down the DMA
mapping of the received packet.

Remove the comment about the descriptor being zeroed as it is no longer
correct. This is OK because we either use the descriptor as-is (when
recycling) or overwrite its address and size fields with that of the
newly allocated Rx buffer.

The issue was discovered when a process ("perf") consumed too much
memory and put the system under memory pressure. It can be reproduced by
injecting slab allocation failures [1]. After the fix, the Rx queue no
longer comes to a halt.

[1]
 # echo 10 > /sys/kernel/debug/failslab/times
 # echo 1000 > /sys/kernel/debug/failslab/interval
 # echo 100 > /sys/kernel/debug/failslab/probability

 FAULT_INJECTION: forcing a failure.
 name failslab, interval 1000, probability 100, space 0, times 8
 [...]
 Call Trace:
  <IRQ>
  dump_stack_lvl+0x34/0x44
  should_fail.cold+0x32/0x37
  should_failslab+0x5/0x10
  kmem_cache_alloc_node+0x23/0x190
  __alloc_skb+0x1f9/0x280
  __netdev_alloc_skb+0x3a/0x150
  mlxsw_pci_rdq_skb_alloc+0x24/0x90
  mlxsw_pci_cq_tasklet+0x3dc/0x1200
  tasklet_action_common.constprop.0+0x9f/0x100
  __do_softirq+0xb5/0x252
  irq_exit_rcu+0x7a/0xa0
  common_interrupt+0x83/0xa0
  </IRQ>
  asm_common_interrupt+0x1e/0x40
 RIP: 0010:cpuidle_enter_state+0xc8/0x340
 [...]
 mlxsw_spectrum2 0000:06:00.0: Failed to alloc skb for RDQ

Fixes: eda6500a98 ("mlxsw: Add PCI bus implementation")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://lore.kernel.org/r/20211024064014.1060919-1-idosch@idosch.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-10-25 18:21:23 -07:00
arch powerpc fixes for 5.15 #5 2021-10-21 15:30:09 -10:00
block block-5.15-2021-10-17 2021-10-17 19:25:20 -10:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-08-30 12:57:10 -07:00
Documentation Networking fixes for 5.15-rc7, including fixes from netfilter, and can. 2021-10-21 15:36:50 -10:00
drivers mlxsw: pci: Recycle received packet upon allocation failure 2021-10-25 18:21:23 -07:00
fs Two important filesystem fixes, marked for stable. The blocklisted 2021-10-20 10:23:05 -10:00
include Merge branch 'ucount-fixes-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-10-21 17:27:17 -10:00
init bootconfig: init: Fix memblock leak in xbc_make_cmdline() 2021-10-10 22:27:40 -04:00
ipc ipc: remove memcg accounting for sops objects in do_semtimedop() 2021-09-14 10:22:11 -07:00
kernel Merge branch 'ucount-fixes-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-10-21 17:27:17 -10:00
lib linux-kselftest-kunit-fixes-5.15-rc6 2021-10-11 17:25:08 -07:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm memblock: exclude MEMBLOCK_NOMAP regions from kmemleak 2021-10-21 18:30:49 -10:00
net net-sysfs: initialize uid and gid before calling net_ns_get_ownership 2021-10-25 16:17:32 +01:00
samples samples/bpf: Relicense bpf_insn.h as GPL-2.0-only OR BSD-2-Clause 2021-09-29 16:03:55 +02:00
scripts Tracing fixes for 5.15: 2021-10-16 10:51:41 -07:00
security Merge branch 'ucount-fixes-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-10-21 17:27:17 -10:00
sound ALSA: usb-audio: Fix microphone sound on Jieli webcam. 2021-10-19 08:07:01 +02:00
tools fcnal-test: kill hanging ping/nettest binaries on cleanup 2021-10-22 14:03:18 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Remove tlbs_dirty 2021-09-23 11:01:12 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild
Kconfig
MAINTAINERS Char/Misc driver fixes for 5.15-rc6 2021-10-17 17:14:00 -10:00
Makefile Linux 5.15-rc6 2021-10-17 20:00:13 -10:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.