Hi Bjorn, Suman, and others Do you have any comments regarding this patch?
BR Fabien > -----Original Message----- > From: Fabien DESSENNE <[email protected]> > Sent: mercredi 11 septembre 2019 15:57 > To: Ohad Ben-Cohen <[email protected]>; Bjorn Andersson > <[email protected]>; Suman Anna <[email protected]>; Jonathan Corbet > <[email protected]>; [email protected]; linux- > [email protected]; [email protected] > Cc: Fabien DESSENNE <[email protected]>; linux-stm32@st-md- > mailman.stormreply.com > Subject: [PATCH v3] hwspinlock: allow sharing of hwspinlocks > > Allow several clients to request (hwspin_lock_request_specific()) the same > lock. > In addition to that, protect a given lock from being locked > (hwspin_trylock{_...}()) by more that one client at a time. > > Since the RAW and IN_ATOMIC modes do not implement that protection (unlike > the default, IRQ and IRQSTATE modes that make use of spin_lock{_irq, > _irqsave}), protect __hwspin_trylock with the atomic bitop test_and_set_bit(). > This bitop is atomic (SMP-safe), does not disable neither preemption nor > interrupts, hence it preserves the RAW and IN_ATOMIC modes constraints. > > Signed-off-by: Fabien Dessenne <[email protected]> > --- > Changes since v2: > - Drop the DeviceTree-based implementation. > - Do not let the choice between exclusive and shared usage : locks are > always shared. > - Add a protection (atomic bitop) working in any modes to allow safe > sharing between clients. > > Changes since v1: > - Removed useless 'status = "okay"' from stm32mp157c.dtsi > --- > Documentation/hwspinlock.txt | 9 ++- > drivers/hwspinlock/hwspinlock_core.c | 98 +++++++++++++++++++++++------ > --- > drivers/hwspinlock/hwspinlock_internal.h | 4 ++ > 3 files changed, 81 insertions(+), 30 deletions(-) > > diff --git a/Documentation/hwspinlock.txt b/Documentation/hwspinlock.txt index > 6f03713..5f6f660 100644 > --- a/Documentation/hwspinlock.txt > +++ b/Documentation/hwspinlock.txt > @@ -53,9 +53,8 @@ Should be called from a process context (might sleep). > > struct hwspinlock *hwspin_lock_request_specific(unsigned int id); > > -Assign a specific hwspinlock id and return its address, or NULL -if that > hwspinlock is already in use. Usually board code will -be calling this > function in > order to reserve specific hwspinlock > +Assign a specific hwspinlock id and return its address. Usually board > +code will be calling this function in order to reserve specific > +hwspinlock > ids for predefined purposes. > > Should be called from a process context (might sleep). > @@ -449,11 +448,15 @@ of which represents a single hardware lock:: > * struct hwspinlock - this struct represents a single hwspinlock > instance > * @bank: the hwspinlock_device structure which owns this lock > * @lock: initialized and used by hwspinlock core > + * @is_locked: whether this lock is currently locked > + * @reqcount: number of users having requested this lock > * @priv: private data, owned by the underlying platform-specific > hwspinlock drv > */ > struct hwspinlock { > struct hwspinlock_device *bank; > spinlock_t lock; > + unsigned long is_locked; > + unsigned int reqcount; > void *priv; > }; > > diff --git a/drivers/hwspinlock/hwspinlock_core.c > b/drivers/hwspinlock/hwspinlock_core.c > index 8862445..e9d3de10 100644 > --- a/drivers/hwspinlock/hwspinlock_core.c > +++ b/drivers/hwspinlock/hwspinlock_core.c > @@ -29,6 +29,7 @@ > > /* radix tree tags */ > #define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */ > +#define HWSPINLOCK_DYN_ASSIGN (1) /* dynamically assigned > hwspinlock */ > > /* > * A radix tree is used to maintain the available hwspinlock instances. > @@ -96,14 +97,25 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int > mode, unsigned long *flags) > BUG_ON(!flags && mode == HWLOCK_IRQSTATE); > > /* > + * Check if the lock is already taken by another context on the local > + * cpu. > + * Calling atomic test_and_set_bit_lock() ensures that hwspinlock is > + * SMP-safe (so we can take it from additional contexts on the local > + * host) in any mode, even those where we do not make use of the local > + * spinlock. > + */ > + > + if (test_and_set_bit_lock(0, &hwlock->is_locked)) > + return -EBUSY; > + > + /* > * This spin_lock{_irq, _irqsave} serves three purposes: > * > * 1. Disable preemption, in order to minimize the period of time > * in which the hwspinlock is taken. This is important in order > * to minimize the possible polling on the hardware interconnect > * by a remote user of this lock. > - * 2. Make the hwspinlock SMP-safe (so we can take it from > - * additional contexts on the local host). > + * 2. Make the hwspinlock SMP-safe. > * 3. Ensure that in_atomic/might_sleep checks catch potential > * problems with hwspinlock usage (e.g. scheduler checks like > * 'scheduling while atomic' etc.) > @@ -124,9 +136,9 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int > mode, unsigned long *flags) > break; > } > > - /* is lock already taken by another context on the local cpu ? */ > + /* sanity check (this shouldn't happen) */ > if (!ret) > - return -EBUSY; > + goto clear; > > /* try to take the hwspinlock device */ > ret = hwlock->bank->ops->trylock(hwlock); > @@ -149,7 +161,7 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int > mode, unsigned long *flags) > break; > } > > - return -EBUSY; > + goto clear; > } > > /* > @@ -165,6 +177,11 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int > mode, unsigned long *flags) > mb(); > > return 0; > + > +clear: > + /* Clear is_locked */ > + clear_bit_unlock(0, &hwlock->is_locked); > + return -EBUSY; > } > EXPORT_SYMBOL_GPL(__hwspin_trylock); > > @@ -299,6 +316,9 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int > mode, unsigned long *flags) > spin_unlock(&hwlock->lock); > break; > } > + > + /* Clear is_locked set while locking */ > + clear_bit_unlock(0, &hwlock->is_locked); > } > EXPORT_SYMBOL_GPL(__hwspin_unlock); > > @@ -504,7 +524,9 @@ int hwspin_lock_register(struct hwspinlock_device *bank, > struct device *dev, > hwlock = &bank->lock[i]; > > spin_lock_init(&hwlock->lock); > + clear_bit(0, &hwlock->is_locked); > hwlock->bank = bank; > + hwlock->reqcount = 0; > > ret = hwspin_lock_register_single(hwlock, base_id + i); > if (ret) > @@ -664,12 +686,16 @@ static int __hwspin_lock_request(struct hwspinlock > *hwlock) > return ret; > } > > - /* mark hwspinlock as used, should not fail */ > - tmp = radix_tree_tag_clear(&hwspinlock_tree, hwlock_to_id(hwlock), > - HWSPINLOCK_UNUSED); > + /* update reqcount */ > + if (!hwlock->reqcount++) { > + /* first request, mark hwspinlock as used, should not fail */ > + tmp = radix_tree_tag_clear(&hwspinlock_tree, > + hwlock_to_id(hwlock), > + HWSPINLOCK_UNUSED); > > - /* self-sanity check that should never fail */ > - WARN_ON(tmp != hwlock); > + /* self-sanity check that should never fail */ > + WARN_ON(tmp != hwlock); > + } > > return ret; > } > @@ -706,7 +732,7 @@ EXPORT_SYMBOL_GPL(hwspin_lock_get_id); > */ > struct hwspinlock *hwspin_lock_request(void) { > - struct hwspinlock *hwlock; > + struct hwspinlock *hwlock, *tmp; > int ret; > > mutex_lock(&hwspinlock_tree_lock); > @@ -728,6 +754,13 @@ struct hwspinlock *hwspin_lock_request(void) > if (ret < 0) > hwlock = NULL; > > + /* mark this hwspinlock as dynamically assigned */ > + tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock), > + HWSPINLOCK_DYN_ASSIGN); > + > + /* self-sanity check which should never fail */ > + WARN_ON(tmp != hwlock); > + > out: > mutex_unlock(&hwspinlock_tree_lock); > return hwlock; > @@ -764,18 +797,19 @@ struct hwspinlock > *hwspin_lock_request_specific(unsigned int id) > /* sanity check (this shouldn't happen) */ > WARN_ON(hwlock_to_id(hwlock) != id); > > - /* make sure this hwspinlock is unused */ > - ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); > - if (ret == 0) { > - pr_warn("hwspinlock %u is already in use\n", id); > + /* mark as used and power up */ > + ret = __hwspin_lock_request(hwlock); > + if (ret < 0) { > hwlock = NULL; > goto out; > } > > - /* mark as used and power up */ > - ret = __hwspin_lock_request(hwlock); > - if (ret < 0) > - hwlock = NULL; > + /* > + * warn if this lock is also used by another client which got this lock > + * with dynamic assignment using the hwspin_lock_request() API > + */ > + if (radix_tree_tag_get(&hwspinlock_tree, id, > HWSPINLOCK_DYN_ASSIGN)) > + pr_warn("hwspinlock %u is shared with a 'dynamic' user\n", id); > > out: > mutex_unlock(&hwspinlock_tree_lock); > @@ -799,7 +833,7 @@ int hwspin_lock_free(struct hwspinlock *hwlock) { > struct device *dev; > struct hwspinlock *tmp; > - int ret; > + int ret, id; > > if (!hwlock) { > pr_err("invalid hwlock\n"); > @@ -810,30 +844,40 @@ int hwspin_lock_free(struct hwspinlock *hwlock) > mutex_lock(&hwspinlock_tree_lock); > > /* make sure the hwspinlock is used */ > - ret = radix_tree_tag_get(&hwspinlock_tree, hwlock_to_id(hwlock), > - HWSPINLOCK_UNUSED); > + id = hwlock_to_id(hwlock); > + ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); > if (ret == 1) { > dev_err(dev, "%s: hwlock is already free\n", __func__); > dump_stack(); > ret = -EINVAL; > - goto out; > + goto out_unlock; > } > > /* notify the underlying device that power is not needed */ > ret = pm_runtime_put(dev); > if (ret < 0) > - goto out; > + goto out_unlock; > + > + /* update reqcount */ > + if (--hwlock->reqcount) > + goto out_put; > > /* mark this hwspinlock as available */ > - tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock), > - HWSPINLOCK_UNUSED); > + tmp = radix_tree_tag_set(&hwspinlock_tree, id, > HWSPINLOCK_UNUSED); > > /* sanity check (this shouldn't happen) */ > WARN_ON(tmp != hwlock); > > + /* clear the dynamically assigned tag */ > + tmp = radix_tree_tag_clear(&hwspinlock_tree, id, > +HWSPINLOCK_DYN_ASSIGN); > + > + /* self-sanity check which should never fail */ > + WARN_ON(tmp != hwlock); > + > +out_put: > module_put(dev->driver->owner); > > -out: > +out_unlock: > mutex_unlock(&hwspinlock_tree_lock); > return ret; > } > diff --git a/drivers/hwspinlock/hwspinlock_internal.h > b/drivers/hwspinlock/hwspinlock_internal.h > index 9eb6bd0..a3aae55 100644 > --- a/drivers/hwspinlock/hwspinlock_internal.h > +++ b/drivers/hwspinlock/hwspinlock_internal.h > @@ -35,11 +35,15 @@ struct hwspinlock_ops { > * struct hwspinlock - this struct represents a single hwspinlock instance > * @bank: the hwspinlock_device structure which owns this lock > * @lock: initialized and used by hwspinlock core > + * @is_locked: whether this lock is currently locked > + * @reqcount: number of users having requested this lock > * @priv: private data, owned by the underlying platform-specific hwspinlock > drv > */ > struct hwspinlock { > struct hwspinlock_device *bank; > spinlock_t lock; > + unsigned long is_locked; > + unsigned int reqcount; > void *priv; > }; > > -- > 2.7.4
