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Linus Lüssing a8f0c3c39e ath9k: Fix potential interrupt storm on queue reset 
[ Upstream commit 4925642d54 ]

In tests with two Lima boards from 8devices (QCA4531 based) on OpenWrt
19.07 we could force a silent restart of a device with no serial
output when we were sending a high amount of UDP traffic (iperf3 at 80
MBit/s in both directions from external hosts, saturating the wifi and
causing a load of about 4.5 to 6) and were then triggering an
ath9k_queue_reset().

Further debugging showed that the restart was caused by the ath79
watchdog. With disabled watchdog we could observe that the device was
constantly going into ath_isr() interrupt handler and was returning
early after the ATH_OP_HW_RESET flag test, without clearing any
interrupts. Even though ath9k_queue_reset() calls
ath9k_hw_kill_interrupts().

With JTAG we could observe the following race condition:

1) ath9k_queue_reset()
   ...
   -> ath9k_hw_kill_interrupts()
   -> set_bit(ATH_OP_HW_RESET, &common->op_flags);
   ...
   <- returns

      2) ath9k_tasklet()
         ...
         -> ath9k_hw_resume_interrupts()
         ...
         <- returns

                 3) loops around:
                    ...
                    handle_int()
                    -> ath_isr()
                       ...
                       -> if (test_bit(ATH_OP_HW_RESET,
                                       &common->op_flags))
                            return IRQ_HANDLED;

                    x) ath_reset_internal():
                       => never reached <=

And in ath_isr() we would typically see the following interrupts /
interrupt causes:

* status: 0x00111030 or 0x00110030
* async_cause: 2 (AR_INTR_MAC_IPQ)
* sync_cause: 0

So the ath9k_tasklet() reenables the ath9k interrupts
through ath9k_hw_resume_interrupts() which ath9k_queue_reset() had just
disabled. And ath_isr() then keeps firing because it returns IRQ_HANDLED
without actually clearing the interrupt.

To fix this IRQ storm also clear/disable the interrupts again when we
are in reset state.

Cc: Sven Eckelmann <sven@narfation.org>
Cc: Simon Wunderlich <sw@simonwunderlich.de>
Cc: Linus Lüssing <linus.luessing@c0d3.blue>
Fixes: 872b5d814f ("ath9k: do not access hardware on IRQs during reset")
Signed-off-by: Linus Lüssing <ll@simonwunderlich.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210914192515.9273-3-linus.luessing@c0d3.blue
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-11-18 19:16:30 +01:00
arch arm64: mm: update max_pfn after memory hotplug 2021-11-18 19:16:27 +01:00
block block: remove inaccurate requeue check 2021-11-18 19:16:17 +01:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: ecc - fix CRYPTO_DEFAULT_RNG dependency 2021-11-18 19:16:29 +01:00
Documentation fscrypt: allow 256-bit master keys with AES-256-XTS 2021-11-18 19:16:11 +01:00
drivers ath9k: Fix potential interrupt storm on queue reset 2021-11-18 19:16:30 +01:00
fs erofs: don't trigger WARN() when decompression fails 2021-11-18 19:16:21 +01:00
include fortify: Fix dropped strcpy() compile-time write overflow check 2021-11-18 19:16:25 +01:00
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 kprobes: Do not use local variable when creating debugfs file 2021-11-18 19:16:29 +01:00
lib bpf/tests: Fix error in tail call limit tests 2021-11-18 19:16:26 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm kfence: always use static branches to guard kfence_alloc() 2021-11-12 15:05:49 +01:00
net cfg80211: always free wiphy specific regdomain 2021-11-18 19:16:26 +01:00
samples samples/bpf: Fix application of sizeof to pointer 2021-11-18 19:16:18 +01:00
scripts leaking_addresses: Always print a trailing newline 2021-11-18 19:16:16 +01:00
security smackfs: use __GFP_NOFAIL for smk_cipso_doi() 2021-11-18 19:16:19 +01:00
sound ASoC: tegra: Restore AC97 support 2021-11-18 19:16:01 +01:00
tools libbpf: Fix skel_internal.h to set errno on loader retval < 0 2021-11-18 19:16:27 +01:00
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 Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.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 COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS drm fixes for 5.15 final 2021-10-28 12:17:01 -07:00
Makefile Linux 5.15.2 2021-11-12 15:05:52 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.