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Ido Schimmel c9ebea04cb mlxsw: pci: Ring CQ's doorbell before RDQ's
When a packet should be trapped to the CPU the device consumes a WQE
(work queue element) from an RDQ (receive descriptor queue) and copies
the packet to the address specified in the WQE. The device then tries to
post a CQE (completion queue element) that contains various metadata
(e.g., ingress port) about the packet to a CQ (completion queue).

In case the device managed to consume a WQE, but did not manage to post
the corresponding CQE, it will get stuck. This unlikely situation can be
triggered due to the scheme the driver is currently using to process
CQEs.

The driver will consume up to 512 CQEs at a time and after processing
each corresponding WQE it will ring the RDQ's doorbell, letting the
device know that a new WQE was posted for it to consume. Only after
processing all the CQEs (up to 512), the driver will ring the CQ's
doorbell, letting the device know that new ones can be posted.

Fix this by having the driver ring the CQ's doorbell for every processed
CQE, but before ringing the RDQ's doorbell. This guarantees that
whenever we post a new WQE, there is a corresponding CQE available. Copy
the currently processed CQE to prevent the device from overwriting it
with a new CQE after ringing the doorbell.

Note that the driver still arms the CQ only after processing all the
pending CQEs, so that interrupts for this CQ will only be delivered
after the driver finished its processing.

Before commit 8404f6f2e8 ("mlxsw: pci: Allow to use CQEs of version 1
and version 2") the issue was virtually impossible to trigger since the
number of CQEs was twice the number of WQEs and the number of CQEs
processed at a time was equal to the number of available WQEs.

Fixes: 8404f6f2e8 ("mlxsw: pci: Allow to use CQEs of version 1 and version 2")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Semion Lisyansky <semionl@mellanox.com>
Tested-by: Semion Lisyansky <semionl@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-01-18 15:12:16 -08:00
arch ARM: SoC fixes 2019-01-14 10:34:14 +12:00
block block: fix kerneldoc comment for blk_attempt_plug_merge() 2019-01-09 15:29:08 -07:00
certs kbuild: remove redundant target cleaning on failure 2019-01-06 09:46:51 +09:00
crypto Kconfig updates for v4.21 2018-12-29 13:03:29 -08:00
Documentation doc: net: fix bad references to network drivers 2019-01-18 11:03:31 -08:00
drivers mlxsw: pci: Ring CQ's doorbell before RDQ's 2019-01-18 15:12:16 -08:00
firmware kbuild: change filechk to surround the given command with { } 2019-01-06 09:46:51 +09:00
fs for-5.0-rc1-tag 2019-01-14 05:55:51 +12:00
include net: Fix usage of pskb_trim_rcsum 2019-01-18 14:05:14 -08:00
init jump_label: move 'asm goto' support test to Kconfig 2019-01-06 09:46:51 +09:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel Andrea Righi fixed a NULL pointer dereference in trace_kprobe_create() 2019-01-16 05:28:26 +12:00
lib sbitmap: Protect swap_lock from hardirq 2019-01-15 16:29:57 +12:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm mm/mmu_notifier: mm/rmap.c: Fix a mmu_notifier range bug in try_to_unmap_one 2019-01-10 02:58:21 -08:00
net net: Fix usage of pskb_trim_rcsum 2019-01-18 14:05:14 -08:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-01-16 05:13:36 +12:00
scripts remove dma_zalloc_coherent 2019-01-12 10:52:40 -08:00
security Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:25:58 -08:00
sound remove dma_zalloc_coherent 2019-01-12 10:52:40 -08:00
tools selftests: tc-testing: fix parsing of ife type 2019-01-16 14:05:42 -08:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt KVM: validate userspace input in kvm_clear_dirty_log_protect() 2019-01-11 18:38:07 +01:00
.clang-format page cache: Convert find_get_pages_contig to XArray 2018-10-21 10:46:34 -04:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap A few early MIPS fixes for 4.21: 2019-01-05 12:48:25 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Add CREDITS entry for Shaohua Li 2019-01-04 14:27:09 -07:00
Kbuild kbuild: use assignment instead of define ... endef for filechk_* rules 2019-01-06 10:22:35 +09:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS MAINTAINERS: update email addresses of liquidio driver maintainers 2019-01-18 14:07:06 -08:00
Makefile Linux 5.0-rc2 2019-01-14 10:41:12 +12:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.