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regulator: core: Make regulator_lock_two() logic easier to follow 

The regulator_lock_two() function could be made clearer in the case of
lock contention by having a local variable for each of the held and
contended locks. Let's do that. At the same time, let's use the swap()
function instead of open coding it.

This change is expected to be a no-op and simply improves code
clarity.

Suggested-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/CAE-0n53Eb1BeDPmjBycXUaQAF4ppiAM6UDWje_jiB9GAmR8MMw@mail.gmail.com
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20230413173359.1.I1ae92b25689bd6579952e6d458b79f5f8054a0c9@changeid
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Douglas Anderson 2023-04-13 17:34:17 -07:00 committed by Mark Brown
parent 902f8c9830
commit 37473397b8
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 10 additions and 17 deletions
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27
drivers/regulator/core.c
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@ -219,7 +219,7 @@ static void regulator_lock_two(struct regulator_dev *rdev1,
struct regulator_dev *rdev2,
struct ww_acquire_ctx *ww_ctx)
{
struct regulator_dev *tmp;
struct regulator_dev *held, *contended;
int ret;
ww_acquire_init(ww_ctx, &regulator_ww_class);
@ -233,25 +233,18 @@ static void regulator_lock_two(struct regulator_dev *rdev1,
goto exit;
}
held = rdev1;
contended = rdev2;
while (true) {
/*
* Start of loop: rdev1 was locked and rdev2 was contended.
* Need to unlock rdev1, slowly lock rdev2, then try rdev1
* again.
*/
regulator_unlock(rdev1);
regulator_unlock(held);
ww_mutex_lock_slow(&rdev2->mutex, ww_ctx);
rdev2->ref_cnt++;
rdev2->mutex_owner = current;
ret = regulator_lock_nested(rdev1, ww_ctx);
ww_mutex_lock_slow(&contended->mutex, ww_ctx);
contended->ref_cnt++;
contended->mutex_owner = current;
swap(held, contended);
ret = regulator_lock_nested(contended, ww_ctx);
if (ret == -EDEADLOCK) {
/* More contention; swap which needs to be slow */
tmp = rdev1;
rdev1 = rdev2;
rdev2 = tmp;
} else {
if (ret != -EDEADLOCK) {
WARN_ON(ret);
break;
}