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67d93ffc0f
vclocks were using spinlocks to protect access to its timecounter and
cyclecounter. Access to timecounter/cyclecounter is backed by the same
driver callbacks that are used for non-virtual PHCs, but the usage of
the spinlock imposes a new limitation that didn't exist previously: now
they're called in atomic context so they mustn't sleep.
Some drivers like sfc or ice may sleep on these callbacks, causing
errors like "BUG: scheduling while atomic: ptp5/25223/0x00000002"
Fix it replacing the vclock's spinlock by a mutex. It fix the mentioned
bug and it doesn't introduce longer delays.
I've tested synchronizing various different combinations of clocks:
- vclock->sysclock
- sysclock->vclock
- vclock->vclock
- hardware PHC in different NIC -> vclock
- created 4 vclocks and launch 4 parallel phc2sys processes with
lockdep enabled
In all cases, comparing the delays reported by phc2sys, they are in the
same range of values than before applying the patch.
Link: https://lore.kernel.org/netdev/69d0ff33-bd32-6aa5-d36c-fbdc3c01337c@redhat.com/
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 | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .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 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.