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hwspinlock/core: use a mutex to protect the radix tree

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Since we're using non-atomic radix tree allocations, we
should be protecting the tree using a mutex and not a
spinlock.

Non-atomic allocations and process context locking is good enough,
as the tree is manipulated only when locks are registered/
unregistered/requested/freed.

The locks themselves are still protected by spinlocks of course,
and mutexes are not involved in the locking/unlocking paths.

Cc: <[email protected]>
Signed-off-by: Juan Gutierrez <[email protected]>
[[email protected]: rewrite the commit log, #include mutex.h, add minor
commentary]
[[email protected]: update register/unregister parts in hwspinlock.txt]
Signed-off-by: Ohad Ben-Cohen <[email protected]>
This commit is contained in:
Juan Gutierrez 2011-09-06 09:30:16 +03:00 • committed by Ohad Ben-Cohen
commit 93b465c2e1
2 changed files with 27 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

45
drivers/hwspinlock/hwspinlock_core.c
View file

@ -26,6 +26,7 @@
#include <linux/radix-tree.h>
#include <linux/hwspinlock.h>
#include <linux/pm_runtime.h>
#include <linux/mutex.h>
#include "hwspinlock_internal.h"
@ -52,10 +53,12 @@
static RADIX_TREE(hwspinlock_tree, GFP_KERNEL);
/*
* Synchronization of access to the tree is achieved using this spinlock,
* Synchronization of access to the tree is achieved using this mutex,
* as the radix-tree API requires that users provide all synchronisation.
* A mutex is needed because we're using non-atomic radix tree allocations.
*/
static DEFINE_SPINLOCK(hwspinlock_tree_lock);
static DEFINE_MUTEX(hwspinlock_tree_lock);
/**
* __hwspin_trylock() - attempt to lock a specific hwspinlock
@ -261,8 +264,7 @@ EXPORT_SYMBOL_GPL(__hwspin_unlock);
* This function should be called from the underlying platform-specific
* implementation, to register a new hwspinlock instance.
*
* Can be called from an atomic context (will not sleep) but not from
* within interrupt context.
* Should be called from a process context (might sleep)
*
* Returns 0 on success, or an appropriate error code on failure
*/
@ -279,7 +281,7 @@ int hwspin_lock_register(struct hwspinlock *hwlock)
spin_lock_init(&hwlock->lock);
spin_lock(&hwspinlock_tree_lock);
mutex_lock(&hwspinlock_tree_lock);
ret = radix_tree_insert(&hwspinlock_tree, hwlock->id, hwlock);
if (ret == -EEXIST)
@ -295,7 +297,7 @@ int hwspin_lock_register(struct hwspinlock *hwlock)
WARN_ON(tmp != hwlock);
out:
spin_unlock(&hwspinlock_tree_lock);
mutex_unlock(&hwspinlock_tree_lock);
return ret;
}
EXPORT_SYMBOL_GPL(hwspin_lock_register);
@ -307,8 +309,7 @@ EXPORT_SYMBOL_GPL(hwspin_lock_register);
* This function should be called from the underlying platform-specific
* implementation, to unregister an existing (and unused) hwspinlock.
*
* Can be called from an atomic context (will not sleep) but not from
* within interrupt context.
* Should be called from a process context (might sleep)
*
* Returns the address of hwspinlock @id on success, or NULL on failure
*/
@ -317,7 +318,7 @@ struct hwspinlock *hwspin_lock_unregister(unsigned int id)
struct hwspinlock *hwlock = NULL;
int ret;
spin_lock(&hwspinlock_tree_lock);
mutex_lock(&hwspinlock_tree_lock);
/* make sure the hwspinlock is not in use (tag is set) */
ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
@ -333,7 +334,7 @@ struct hwspinlock *hwspin_lock_unregister(unsigned int id)
}
out:
spin_unlock(&hwspinlock_tree_lock);
mutex_unlock(&hwspinlock_tree_lock);
return hwlock;
}
EXPORT_SYMBOL_GPL(hwspin_lock_unregister);
@ -402,9 +403,7 @@ EXPORT_SYMBOL_GPL(hwspin_lock_get_id);
* to the remote core before it can be used for synchronization (to get the
* id of a given hwlock, use hwspin_lock_get_id()).
*
* Can be called from an atomic context (will not sleep) but not from
* within interrupt context (simply because there is no use case for
* that yet).
* Should be called from a process context (might sleep)
*
* Returns the address of the assigned hwspinlock, or NULL on error
*/
@ -413,7 +412,7 @@ struct hwspinlock *hwspin_lock_request(void)
struct hwspinlock *hwlock;
int ret;
spin_lock(&hwspinlock_tree_lock);
mutex_lock(&hwspinlock_tree_lock);
/* look for an unused lock */
ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock,
@ -433,7 +432,7 @@ struct hwspinlock *hwspin_lock_request(void)
hwlock = NULL;
out:
spin_unlock(&hwspinlock_tree_lock);
mutex_unlock(&hwspinlock_tree_lock);
return hwlock;
}
EXPORT_SYMBOL_GPL(hwspin_lock_request);
@ -447,9 +446,7 @@ EXPORT_SYMBOL_GPL(hwspin_lock_request);
* Usually early board code will be calling this function in order to
* reserve specific hwspinlock ids for predefined purposes.
*
* Can be called from an atomic context (will not sleep) but not from
* within interrupt context (simply because there is no use case for
* that yet).
* Should be called from a process context (might sleep)
*
* Returns the address of the assigned hwspinlock, or NULL on error
*/
@ -458,7 +455,7 @@ struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
struct hwspinlock *hwlock;
int ret;
spin_lock(&hwspinlock_tree_lock);
mutex_lock(&hwspinlock_tree_lock);
/* make sure this hwspinlock exists */
hwlock = radix_tree_lookup(&hwspinlock_tree, id);
@ -484,7 +481,7 @@ struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
hwlock = NULL;
out:
spin_unlock(&hwspinlock_tree_lock);
mutex_unlock(&hwspinlock_tree_lock);
return hwlock;
}
EXPORT_SYMBOL_GPL(hwspin_lock_request_specific);
@ -497,9 +494,7 @@ EXPORT_SYMBOL_GPL(hwspin_lock_request_specific);
* Should only be called with an @hwlock that was retrieved from
* an earlier call to omap_hwspin_lock_request{_specific}.
*
* Can be called from an atomic context (will not sleep) but not from
* within interrupt context (simply because there is no use case for
* that yet).
* Should be called from a process context (might sleep)
*
* Returns 0 on success, or an appropriate error code on failure
*/
@ -513,7 +508,7 @@ int hwspin_lock_free(struct hwspinlock *hwlock)
return -EINVAL;
}
spin_lock(&hwspinlock_tree_lock);
mutex_lock(&hwspinlock_tree_lock);
/* make sure the hwspinlock is used */
ret = radix_tree_tag_get(&hwspinlock_tree, hwlock->id,
@ -540,7 +535,7 @@ int hwspin_lock_free(struct hwspinlock *hwlock)
module_put(hwlock->dev->driver->owner);
out:
spin_unlock(&hwspinlock_tree_lock);
mutex_unlock(&hwspinlock_tree_lock);
return ret;
}
EXPORT_SYMBOL_GPL(hwspin_lock_free);