Messages in this thread | | | Date | Fri, 1 Sep 2023 00:41:32 +0200 | From | Michał Mirosław <> | Subject | Re: [PATCH v2 3/7] regulator/core: regulator_lock_nested: simplify nested locking |
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On Wed, Aug 30, 2023 at 01:54:21PM -0700, Doug Anderson wrote: > On Wed, Aug 30, 2023 at 10:35 AM Michał Mirosław > <mirq-linux@rere.qmqm.pl> wrote: > > > > Simplify regulator locking by removing locking around locking. > > rdev->ref check when unlocking is moved inside the critical section. > > > > This patch depends on commit 12235da8c80a ("kernel/locking: Add context > > to ww_mutex_trylock()"). > > > > Note: return -EALREADY is removed as no caller depends on it and in that > > case the lock count is incremented anyway. > > > > Reviewed-by: Douglas Anderson <dianders@chromium.org> > > Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> > > --- > > drivers/regulator/core.c | 23 ++++++----------------- > > 1 file changed, 6 insertions(+), 17 deletions(-) > > Note that I didn't actually provide a Reviewed-by on this patch in v1. > I was hoping for something in the commit message that explained why > commit 12235da8c80a ("kernel/locking: Add context to > ww_mutex_trylock()") meant that we didn't need the extra lock. You > responded to the v1, but didn't add anything to the commit message > about it. > > Looking at your response to v1, I'm not sure it helps enlighten me on > why adding the context removed the need for the extra lock. Can you > add more words? Pretend I don't know anything about ww_mutex, which is > not far from the truth since every time I look at ww_mutex I have to > re-learn how it works. :-P Specifically, what would actually have been
Thanks for all your (and Stephen's) questions and comments! I had a bit more of thinking and reading time about the W/W mutex and how it works. It turns out I can remove some noise from this commit.
The commit 12235da8c80a dependency is due to text changes: the original code would need a bit of reordering, all not much different than the two previous patches.
If ww_mutex_lock() was able to return -EALREADY with NULL ww_ctx, regulator_lock_nested() could be made even simpler.
Best Regards, Michał Mirosław
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