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4d4d9ef9df
Resolve the budget negative overflow which leads to returning true in
ixgbe_xmit_zc even when the budget of descs are thoroughly consumed.
Before this patch, when the budget is decreased to zero and finishes
sending the last allowed desc in ixgbe_xmit_zc, it will always turn back
and enter into the while() statement to see if it should keep processing
packets, but in the meantime it unexpectedly decreases the value again to
'unsigned int (0--)', namely, UINT_MAX. Finally, the ixgbe_xmit_zc returns
true, showing 'we complete cleaning the budget'. That also means
'clean_complete = true' in ixgbe_poll.
The true theory behind this is if that budget number of descs are consumed,
it implies that we might have more descs to be done. So we should return
false in ixgbe_xmit_zc to tell napi poll to find another chance to start
polling to handle the rest of descs. On the contrary, returning true here
means job done and we know we finish all the possible descs this time and
we don't intend to start a new napi poll.
It is apparently against our expectations. Please also see how
ixgbe_clean_tx_irq() handles the problem: it uses do..while() statement
to make sure the budget can be decreased to zero at most and the negative
overflow never happens.
The patch adds 'likely' because we rarely would not hit the loop condition
since the standard budget is 256.
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| 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 reStructuredText 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.