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hwmon: submitting-patches: Explain race conditions caused by calculations in macros

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The current documentation advises against calculations in macros
primarily to avoid code obfuscation. It misses the risk of concurrency
issues.

Add a note explaining that macros evaluating arguments multiple times
can lead to race conditions when accessing shared data.

Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@mail.gmail.com/
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
Link: https://lore.kernel.org/r/20251202175536.12774-1-hanguidong02@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Gui-Dong Han 2025-12-03 01:55:36 +08:00 • committed by Guenter Roeck
parent 615901b57b
commit d0a0960602
1 changed files with 4 additions and 1 deletions
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5
Documentation/hwmon/submitting-patches.rst
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@ -82,7 +82,10 @@ increase the chances of your change being accepted.
* Avoid calculations in macros and macro-generated functions. While such macros
may save a line or so in the source, it obfuscates the code and makes code
review more difficult. It may also result in code which is more complicated
than necessary. Use inline functions or just regular functions instead.
than necessary. Such macros may also evaluate their arguments multiple times.
This leads to Time-of-Check to Time-of-Use (TOCTOU) race conditions when
accessing shared data without locking, for example when calculating values in
sysfs show functions. Use inline functions or just regular functions instead.
* Limit the number of kernel log messages. In general, your driver should not
generate an error message just because a runtime operation failed. Report