Messages in this thread | | | Subject | Re: [PATCH] regulator: core: avoid regulator_resolve_supply() race condition | From | David Collins <> | Date | Fri, 22 Jan 2021 17:54:56 -0800 |
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Hello Mark,
On 1/21/21 12:30 PM, Marek Szyprowski wrote: > Hi Mark, > > On 21.01.2021 16:44, Mark Brown wrote: >> On Thu, Jan 21, 2021 at 10:41:59AM +0100, Marek Szyprowski wrote: >>> On 18.01.2021 21:49, Mark Brown wrote: >>>> Does this help (completely untested): >>> Sadly nope. I get same warning: >> Try this instead: >> >> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c >> index 3ae5ccd9277d..31503776dbd7 100644 >> --- a/drivers/regulator/core.c >> +++ b/drivers/regulator/core.c >> @@ -1823,17 +1823,6 @@ static int regulator_resolve_supply(struct regulator_dev *rdev) >> if (rdev->supply) >> return 0; >> >> - /* >> - * Recheck rdev->supply with rdev->mutex lock held to avoid a race >> - * between rdev->supply null check and setting rdev->supply in >> - * set_supply() from concurrent tasks. >> - */ >> - regulator_lock(rdev); >> - >> - /* Supply just resolved by a concurrent task? */ >> - if (rdev->supply) >> - goto out; >> - >> r = regulator_dev_lookup(dev, rdev->supply_name); >> if (IS_ERR(r)) { >> ret = PTR_ERR(r); >> @@ -1885,12 +1874,29 @@ static int regulator_resolve_supply(struct regulator_dev *rdev) >> goto out; >> } >> >> + /* >> + * Recheck rdev->supply with rdev->mutex lock held to avoid a race >> + * between rdev->supply null check and setting rdev->supply in >> + * set_supply() from concurrent tasks. >> + */ >> + regulator_lock(rdev); >> + >> + /* Supply just resolved by a concurrent task? */ >> + if (rdev->supply) { >> + regulator_unlock(rdev); >> + put_device(&r->dev); >> + return ret; >> + } >> + >> ret = set_supply(rdev, r); >> if (ret < 0) { >> + regulator_unlock(rdev); >> put_device(&r->dev); >> - goto out; >> + return ret; >> } >> >> + regulator_unlock(rdev); >> + >> /* >> * In set_machine_constraints() we may have turned this regulator on >> * but we couldn't propagate to the supply if it hadn't been resolved >> @@ -1901,12 +1907,11 @@ static int regulator_resolve_supply(struct regulator_dev *rdev) >> if (ret < 0) { >> _regulator_put(rdev->supply); >> rdev->supply = NULL; >> - goto out; >> + goto out_rdev_lock; > > drivers/regulator/core.c:1910:4: error: label ‘out_rdev_lock’ used but > not defined > >> } >> } >> >> out: >> - regulator_unlock(rdev); >> return ret; >> } >> > > It looks that it finally fixes the locking issue, with the above goto > removed completely to fix build. Feel free to add: > > Reported-by: Marek Szyprowski <m.szyprowski@samsung.com> > > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Thank you for making this fix. I'm sorry that I missed the potential deadlock issue resulting from the regulator_enable() call inside regulator_resolve_supply() with rdev->mutex locked. Your fix avoids deadlock while still ensuring that the there isn't a set supply race condition.
Take care, David
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