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Jacob Keller 30f1587409 ice: fix handling of burst Tx timestamps 
Commit 1229b33973 ("ice: Add low latency Tx timestamp read") refactored
PTP timestamping logic to use a threaded IRQ instead of a separate kthread.

This implementation introduced ice_misc_intr_thread_fn and redefined the
ice_ptp_process_ts function interface to return a value of whether or not
the timestamp processing was complete.

ice_misc_intr_thread_fn would take the return value from ice_ptp_process_ts
and convert it into either IRQ_HANDLED if there were no more timestamps to
be processed, or IRQ_WAKE_THREAD if the thread should continue processing.

This is not correct, as the kernel does not re-schedule threaded IRQ
functions automatically. IRQ_WAKE_THREAD can only be used by the main IRQ
function.

This results in the ice_ptp_process_ts function (and in turn the
ice_ptp_tx_tstamp function) from only being called exactly once per
interrupt.

If an application sends a burst of Tx timestamps without waiting for a
response, the interrupt will trigger for the first timestamp. However,
later timestamps may not have arrived yet. This can result in dropped or
discarded timestamps. Worse, on E822 hardware this results in the interrupt
logic getting stuck such that no future interrupts will be triggered. The
result is complete loss of Tx timestamp functionality.

Fix this by modifying the ice_misc_intr_thread_fn to perform its own
polling of the ice_ptp_process_ts function. We sleep for a few microseconds
between attempts to avoid wasting significant CPU time. The value was
chosen to allow time for the Tx timestamps to complete without wasting so
much time that we overrun application wait budgets in the worst case.

The ice_ptp_process_ts function also currently returns false in the event
that the Tx tracker is not initialized. This would result in the threaded
IRQ handler never exiting if it gets started while the tracker is not
initialized.

Fix the function to appropriately return true when the tracker is not
initialized.

Note that this will not reproduce with default ptp4l behavior, as the
program always synchronously waits for a timestamp response before sending
another timestamp request.

Reported-by: Siddaraju DH <siddaraju.dh@intel.com>
Fixes: 1229b33973 ("ice: Add low latency Tx timestamp read")
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20221118222729.1565317-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-11-21 20:50:35 -08:00
arch Networking fixes for 6.1-rc6, including fixes from bpf 2022-11-17 08:58:36 -08:00
block block-6.1-2022-11-11 2022-11-11 14:08:30 -08:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto treewide: use get_random_bytes() when possible 2022-10-11 17:42:58 -06:00
Documentation 22 hotfixes. 8 are cc:stable and the remainder address issues which were 2022-11-11 17:18:42 -08:00
drivers ice: fix handling of burst Tx timestamps 2022-11-21 20:50:35 -08:00
fs netfslib fixes 2022-11-15 14:56:23 -08:00
include net: neigh: decrement the family specific qlen 2022-11-18 10:29:50 +00:00
init init: Kconfig: fix spelling mistake "satify" -> "satisfy" 2022-10-20 21:27:22 -07:00
io_uring io_uring/poll: lockdep annote io_poll_req_insert_locked 2022-11-11 09:59:27 -07:00
ipc ipc/msg.c: fix percpu_counter use after free 2022-10-28 13:37:22 -07:00
kernel Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2022-11-11 18:27:40 -08:00
lib maple_tree: don't set a new maximum on the node when not reusing nodes 2022-11-08 15:57:25 -08:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm Networking fixes for 6.1-rc6, including fixes from bpf 2022-11-17 08:58:36 -08:00
net tipc: check skb_linearize() return value in tipc_disc_rcv() 2022-11-21 20:50:24 -08:00
rust Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
samples VFIO updates for v6.1-rc1 2022-10-12 14:46:48 -07:00
scripts s390 updates for 6.1-rc5 2022-11-11 11:49:20 -08:00
security lsm/stable-6.1 PR 20221031 2022-10-31 12:09:42 -07:00
sound ALSA: memalloc: Try dma_alloc_noncontiguous() at first 2022-11-12 09:48:51 +01:00
tools selftests/net: Find nettest in current directory 2022-11-21 12:58:26 +00:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt Merge tag 'kvmarm-fixes-6.1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD 2022-11-06 03:30:49 -05:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap mailmap: update email for Qais Yousef 2022-10-20 21:27:21 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Vivien to CREDITS 2022-11-10 13:53:53 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS hyperv-fixes for v6.1-rc5 2022-11-11 09:24:03 -08:00
Makefile Linux 6.1-rc5 2022-11-13 13:12:55 -08:00
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.