| Message ID | 1568210227-32135-1-git-send-email-fabien.dessenne@st.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] hwspinlock: allow sharing of hwspinlocks | expand |
Hi Bjorn, Suman, and others Do you have any comments regarding this patch? BR Fabien > -----Original Message----- > From: Fabien DESSENNE <fabien.dessenne@st.com> > Sent: mercredi 11 septembre 2019 15:57 > To: Ohad Ben-Cohen <ohad@wizery.com>; Bjorn Andersson > <bjorn.andersson@linaro.org>; Suman Anna <s-anna@ti.com>; Jonathan Corbet > <corbet@lwn.net>; linux-remoteproc@vger.kernel.org; linux- > doc@vger.kernel.org; linux-kernel@vger.kernel.org > Cc: Fabien DESSENNE <fabien.dessenne@st.com>; 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 <fabien.dessenne@st.com> > --- > 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
Hi
Feel free to share your comments :)
As a reminder, below are two examples that explain the need for this patch.
In both cases the Linux clients are talking to a single entity on the
remote-side.
Example 1:
exti: interrupt-controller@5000d000 {
compatible = "st,stm32mp1-exti", "syscon";
hwlocks = <&hsem 1>;
...
};
The two drivers (stm32mp1-exti and syscon) refer to the same hwlock.
With the current hwspinlock implementation, only the first driver
succeeds in requesting (hwspin_lock_request_specific) the hwlock. The
second request fails.
Example 2:
Here it is more a question of optimization : we want to save the number
of hwlocks used to protect resources, using an unique hwlock to protect
all pinctrl resources:
pinctrl: pin-controller@50002000 {
compatible = "st,stm32mp157-pinctrl";
hwlocks = <&hsem 0 1>;
...
pinctrl_z: pin-controller-z@54004000 {
compatible = "st,stm32mp157-z-pinctrl";
hwlocks = <&hsem 0 1>;
...
BR
Fabien
On 10/10/2019 5:19 PM, Fabien DESSENNE wrote:
> Hi Bjorn, Suman, and others
>
> Do you have any comments regarding this patch?
>
> BR
> Fabien
>
>
>> -----Original Message-----
>> From: Fabien DESSENNE <fabien.dessenne@st.com>
>> Sent: mercredi 11 septembre 2019 15:57
>> To: Ohad Ben-Cohen <ohad@wizery.com>; Bjorn Andersson
>> <bjorn.andersson@linaro.org>; Suman Anna <s-anna@ti.com>; Jonathan Corbet
>> <corbet@lwn.net>; linux-remoteproc@vger.kernel.org; linux-
>> doc@vger.kernel.org; linux-kernel@vger.kernel.org
>> Cc: Fabien DESSENNE <fabien.dessenne@st.com>; 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 <fabien.dessenne@st.com>
>> ---
>> 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
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; };
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 <fabien.dessenne@st.com> --- 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(-)