On Mon, Sep 15, 2025 at 10:40 PM Sebastian Andrzej Siewior <[email protected]> wrote: > > On 2025-09-15 21:47:29 [+0800], pengdonglin wrote: > > From: pengdonglin <[email protected]> > > > > Per Documentation/RCU/rcu_dereference.rst [1], since Linux 4.20's RCU > > consolidation [2][3], RCU read-side critical sections include: > > - Explicit rcu_read_lock() > > - BH/interrupt/preemption-disabling regions > > - Spinlock critical sections (including CONFIG_PREEMPT_RT kernels [4]) > > > > Thus, explicit rcu_read_lock()/unlock() calls within spin_lock*() regions > > are redundant. > > This patch removes them, simplifying locking semantics while preserving RCU > > protection. > > > > [1] > > https://elixir.bootlin.com/linux/v6.17-rc5/source/Documentation/RCU/rcu_dereference.rst#L407 > > [2] https://lore.kernel.org/lkml/[email protected]/ > > [3] https://lwn.net/Articles/777036/ > > [4] > > https://lore.kernel.org/lkml/6435833a-bdcb-4114-b29d-28b7f436d47d@paulmck-laptop/ > > What about something like this: > > Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side > function definitions") there is no difference between rcu_read_lock(), > rcu_read_lock_bh() and rcu_read_lock_sched() in terms of RCU read > section and the relevant grace period. That means that spin_lock(), > which implies rcu_read_lock_sched(), also implies rcu_read_lock(). > > There is no need no explicitly start a RCU read section if one has > already been started implicitly by spin_lock(). > > Simplify the code and remove the inner rcu_read_lock() invocation. > > > The description above should make it clear what: > - the intention is > - the proposed solution to it and why it is correct.
Thanks, that's much clearer. I'll use this commit message in v3. > > You can't send a patch like this. You need to split it at the very least > by subsystem. The networking bits need to follow to follow for instance > Documentation/process/maintainer-netdev.rst Thanks, I will split this into a series for v3. > > and so on. > > Sebastian
