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a2b1a5d40b
As reported by Yuming, currently tc always show a latency of UINT_MAX
for netem Qdisc's on 32-bit platforms:
$ tc qdisc add dev dummy0 root netem latency 100ms
$ tc qdisc show dev dummy0
qdisc netem 8001: root refcnt 2 limit 1000 delay 275s 275s
^^^^^^^^^^^^^^^^
Let us take a closer look at netem_dump():
qopt.latency = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->latency,
UINT_MAX);
qopt.latency is __u32, psched_tdiff_t is signed long,
(psched_tdiff_t)(UINT_MAX) is negative for 32-bit platforms, so
qopt.latency is always UINT_MAX.
Fix it by using psched_time_t (u64) instead.
Note: confusingly, users have two ways to specify 'latency':
1. normally, via '__u32 latency' in struct tc_netem_qopt;
2. via the TCA_NETEM_LATENCY64 attribute, which is s64.
For the second case, theoretically 'latency' could be negative. This
patch ignores that corner case, since it is broken (i.e. assigning a
negative s64 to __u32) anyways, and should be handled separately.
Thanks Ted Lin for the analysis [1] .
[1] https://github.com/raspberrypi/linux/issues/3512
Reported-by: Yuming Chen <chenyuming.junnan@bytedance.com>
Fixes:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.