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The commit 625d344978 ("Revert "kernel/printk: add kmsg SEEK_CUR
handling"") reverted a change done to the return value in case a SEEK_CUR
operation was performed for kmsg buffer based on the fact that different
userspace apps were handling the new return value (-ESPIPE) in different
ways, breaking them.
At the same time -ESPIPE was the wrong decision because kmsg /does support/
seek() but doesn't follow the "normal" behavior userspace is used to.
Because of that and also considering the time -EINVAL has been used, it was
decided to keep this way to avoid more userspace breakage.
This patch adds an official statement to the kmsg documentation pointing to
the current return value for SEEK_CUR, -EINVAL, thus userspace libraries
and apps can refer to it for a definitive guide on what to expect.
Signed-off-by: Bruno Meneguele <bmeneg@redhat.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200710174423.10480-1-bmeneg@redhat.com
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.