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When CONFIG_DEBUG_NET_SMALL_RTNL is off, rtnl_net_dereference() is the
static inline wrapper of rtnl_dereference() returning a plain (void *)
pointer to make sure net is always evaluated as requested in [0].
But, it makes sparse complain [1] when the pointer has __rcu annotation:
net/ipv4/devinet.c:674:47: sparse: warning: incorrect type in argument 2 (different address spaces)
net/ipv4/devinet.c:674:47: sparse: expected void *p
net/ipv4/devinet.c:674:47: sparse: got struct in_ifaddr [noderef] __rcu *
Also, if we evaluate net as (void *) in a macro, then the compiler
in turn fails to build due to -Werror=unused-value.
#define rtnl_net_dereference(net, p) \
({ \
(void *)net; \
rtnl_dereference(p); \
})
net/ipv4/devinet.c: In function ‘inet_rtm_deladdr’:
./include/linux/rtnetlink.h:154:17: error: statement with no effect [-Werror=unused-value]
154 | (void *)net; \
net/ipv4/devinet.c:674:21: note: in expansion of macro ‘rtnl_net_dereference’
674 | (ifa = rtnl_net_dereference(net, *ifap)) != NULL;
| ^~~~~~~~~~~~~~~~~~~~
Let's go back to the original simplest macro.
Note that checkpatch complains about this approach, but it's one-shot and
less noisy than the other two.
WARNING: Argument 'net' is not used in function-like macro
#76: FILE: include/linux/rtnetlink.h:142:
+#define rtnl_net_dereference(net, p) \
+ rtnl_dereference(p)
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 | ||
| .editorconfig | ||
| .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 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.