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The per-CPU rcu_data structure's ->cpu_no_qs.b.exp field is updated only on the instance corresponding to the current CPU, but can be read more widely. Unmarked accesses are OK from the corresponding CPU, but only if interrupts are disabled, given that interrupt handlers can and do modify this field. Unfortunately, although the load from rcu_preempt_deferred_qs() is always carried out from the corresponding CPU, interrupts are not necessarily disabled. This commit therefore upgrades this load to READ_ONCE. Similarly, the diagnostic access from synchronize_rcu_expedited_wait() might run with interrupts disabled and from some other CPU. This commit therefore marks this load with data_race(). Finally, the C-language access in rcu_preempt_ctxt_queue() is OK as is because interrupts are disabled and this load is always from the corresponding CPU. This commit adds a comment giving the rationale for this access being safe. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> |
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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.