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This patch modifies the skb_unref function to skip the early return optimization when CONFIG_DEBUG_NET is enabled. The change ensures that the reference count decrement always occurs in debug builds, allowing for more thorough checking of SKB reference counting. Previously, when the SKB's reference count was 1 and CONFIG_DEBUG_NET was not set, the function would return early after a memory barrier (smp_rmb()) without decrementing the reference count. This optimization assumes it's safe to proceed with freeing the SKB without the overhead of an atomic decrement from 1 to 0. With this change: - In non-debug builds (CONFIG_DEBUG_NET not set), behavior remains unchanged, preserving the performance optimization. - In debug builds (CONFIG_DEBUG_NET set), the reference count is always decremented, even when it's 1, allowing for consistent behavior and potentially catching subtle SKB management bugs. This modification enhances debugging capabilities for networking code without impacting performance in production kernels. It helps kernel developers identify and diagnose issues related to SKB management and reference counting in the network stack. Cc: Chris Mason <clm@fb.com> Suggested-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20240729104741.370327-1-leitao@debian.org Signed-off-by: Paolo Abeni <pabeni@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 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.