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

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: <stable@kernel.org>
Signed-off-by: Juan Gutierrez <jgutierrez@ti.com>
[ohad@wizery.com: rewrite the commit log, #include mutex.h, add minor
commentary]
[ohad@wizery.com: update register/unregister parts in hwspinlock.txt]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
This commit is contained in:
Juan Gutierrez 2011-09-06 09:30:16 +03:00 committed by Ohad Ben-Cohen
parent c3c1250e93
commit 93b465c2e1
2 changed files with 27 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
Documentation/hwspinlock.txt
View File

@ -39,23 +39,20 @@ independent, drivers.
in case an unused hwspinlock isn't available. Users of this in case an unused hwspinlock isn't available. Users of this
API will usually want to communicate the lock's id to the remote core API will usually want to communicate the lock's id to the remote core
before it can be used to achieve synchronization. before it can be used to achieve synchronization.
Can be called from an atomic context (this function will not sleep) but Should be called from a process context (might sleep).
not from within interrupt context.
struct hwspinlock *hwspin_lock_request_specific(unsigned int id); struct hwspinlock *hwspin_lock_request_specific(unsigned int id);
- assign a specific hwspinlock id and return its address, or NULL - assign a specific hwspinlock id and return its address, or NULL
if that hwspinlock is already in use. Usually board code will if that hwspinlock is already in use. Usually board code will
be calling this function in order to reserve specific hwspinlock be calling this function in order to reserve specific hwspinlock
ids for predefined purposes. ids for predefined purposes.
Can be called from an atomic context (this function will not sleep) but Should be called from a process context (might sleep).
not from within interrupt context.
int hwspin_lock_free(struct hwspinlock *hwlock); int hwspin_lock_free(struct hwspinlock *hwlock);
- free a previously-assigned hwspinlock; returns 0 on success, or an - free a previously-assigned hwspinlock; returns 0 on success, or an
appropriate error code on failure (e.g. -EINVAL if the hwspinlock appropriate error code on failure (e.g. -EINVAL if the hwspinlock
is already free). is already free).
Can be called from an atomic context (this function will not sleep) but Should be called from a process context (might sleep).
not from within interrupt context.
int hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int timeout); int hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int timeout);
- lock a previously-assigned hwspinlock with a timeout limit (specified in - lock a previously-assigned hwspinlock with a timeout limit (specified in
@ -232,15 +229,14 @@ int hwspinlock_example2(void)
int hwspin_lock_register(struct hwspinlock *hwlock); int hwspin_lock_register(struct hwspinlock *hwlock);
- to be called from the underlying platform-specific implementation, in - to be called from the underlying platform-specific implementation, in
order to register a new hwspinlock instance. Can be called from an atomic order to register a new hwspinlock instance. Should be called from
context (this function will not sleep) but not from within interrupt a process context (this function might sleep).
context. Returns 0 on success, or appropriate error code on failure. Returns 0 on success, or appropriate error code on failure.
struct hwspinlock *hwspin_lock_unregister(unsigned int id); struct hwspinlock *hwspin_lock_unregister(unsigned int id);
- to be called from the underlying vendor-specific implementation, in order - to be called from the underlying vendor-specific implementation, in order
to unregister an existing (and unused) hwspinlock instance. to unregister an existing (and unused) hwspinlock instance.
Can be called from an atomic context (will not sleep) but not from Should be called from a process context (this function might sleep).
within interrupt context.
Returns the address of hwspinlock on success, or NULL on error (e.g. Returns the address of hwspinlock on success, or NULL on error (e.g.
if the hwspinlock is sill in use). if the hwspinlock is sill in use).

45
drivers/hwspinlock/hwspinlock_core.c
View File

@ -26,6 +26,7 @@
#include <linux/radix-tree.h> #include <linux/radix-tree.h>
#include <linux/hwspinlock.h> #include <linux/hwspinlock.h>
#include <linux/pm_runtime.h> #include <linux/pm_runtime.h>
#include <linux/mutex.h>
#include "hwspinlock_internal.h" #include "hwspinlock_internal.h"
@ -52,10 +53,12 @@
static RADIX_TREE(hwspinlock_tree, GFP_KERNEL); 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. * 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 * __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 * This function should be called from the underlying platform-specific
* implementation, to register a new hwspinlock instance. * implementation, to register a new hwspinlock instance.
* *
* Can be called from an atomic context (will not sleep) but not from * Should be called from a process context (might sleep)
* within interrupt context.
* *
* Returns 0 on success, or an appropriate error code on failure * 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_init(&hwlock->lock);
spin_lock(&hwspinlock_tree_lock); mutex_lock(&hwspinlock_tree_lock);
ret = radix_tree_insert(&hwspinlock_tree, hwlock->id, hwlock); ret = radix_tree_insert(&hwspinlock_tree, hwlock->id, hwlock);
if (ret == -EEXIST) if (ret == -EEXIST)
@ -295,7 +297,7 @@ int hwspin_lock_register(struct hwspinlock *hwlock)
WARN_ON(tmp != hwlock); WARN_ON(tmp != hwlock);
out: out:
spin_unlock(&hwspinlock_tree_lock); mutex_unlock(&hwspinlock_tree_lock);
return ret; return ret;
} }
EXPORT_SYMBOL_GPL(hwspin_lock_register); 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 * This function should be called from the underlying platform-specific
* implementation, to unregister an existing (and unused) hwspinlock. * implementation, to unregister an existing (and unused) hwspinlock.
* *
* Can be called from an atomic context (will not sleep) but not from * Should be called from a process context (might sleep)
* within interrupt context.
* *
* Returns the address of hwspinlock @id on success, or NULL on failure * 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; struct hwspinlock *hwlock = NULL;
int ret; int ret;
spin_lock(&hwspinlock_tree_lock); mutex_lock(&hwspinlock_tree_lock);
/* make sure the hwspinlock is not in use (tag is set) */ /* make sure the hwspinlock is not in use (tag is set) */
ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
@ -333,7 +334,7 @@ struct hwspinlock *hwspin_lock_unregister(unsigned int id)
} }
out: out:
spin_unlock(&hwspinlock_tree_lock); mutex_unlock(&hwspinlock_tree_lock);
return hwlock; return hwlock;
} }
EXPORT_SYMBOL_GPL(hwspin_lock_unregister); 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 * to the remote core before it can be used for synchronization (to get the
* id of a given hwlock, use hwspin_lock_get_id()). * id of a given hwlock, use hwspin_lock_get_id()).
* *
* Can be called from an atomic context (will not sleep) but not from * Should be called from a process context (might sleep)
* within interrupt context (simply because there is no use case for
* that yet).
* *
* Returns the address of the assigned hwspinlock, or NULL on error * Returns the address of the assigned hwspinlock, or NULL on error
*/ */
@ -413,7 +412,7 @@ struct hwspinlock *hwspin_lock_request(void)
struct hwspinlock *hwlock; struct hwspinlock *hwlock;
int ret; int ret;
spin_lock(&hwspinlock_tree_lock); mutex_lock(&hwspinlock_tree_lock);
/* look for an unused lock */ /* look for an unused lock */
ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock, ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock,
@ -433,7 +432,7 @@ struct hwspinlock *hwspin_lock_request(void)
hwlock = NULL; hwlock = NULL;
out: out:
spin_unlock(&hwspinlock_tree_lock); mutex_unlock(&hwspinlock_tree_lock);
return hwlock; return hwlock;
} }
EXPORT_SYMBOL_GPL(hwspin_lock_request); 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 * Usually early board code will be calling this function in order to
* reserve specific hwspinlock ids for predefined purposes. * reserve specific hwspinlock ids for predefined purposes.
* *
* Can be called from an atomic context (will not sleep) but not from * Should be called from a process context (might sleep)
* within interrupt context (simply because there is no use case for
* that yet).
* *
* Returns the address of the assigned hwspinlock, or NULL on error * 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; struct hwspinlock *hwlock;
int ret; int ret;
spin_lock(&hwspinlock_tree_lock); mutex_lock(&hwspinlock_tree_lock);
/* make sure this hwspinlock exists */ /* make sure this hwspinlock exists */
hwlock = radix_tree_lookup(&hwspinlock_tree, id); hwlock = radix_tree_lookup(&hwspinlock_tree, id);
@ -484,7 +481,7 @@ struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
hwlock = NULL; hwlock = NULL;
out: out:
spin_unlock(&hwspinlock_tree_lock); mutex_unlock(&hwspinlock_tree_lock);
return hwlock; return hwlock;
} }
EXPORT_SYMBOL_GPL(hwspin_lock_request_specific); 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 * Should only be called with an @hwlock that was retrieved from
* an earlier call to omap_hwspin_lock_request{_specific}. * an earlier call to omap_hwspin_lock_request{_specific}.
* *
* Can be called from an atomic context (will not sleep) but not from * Should be called from a process context (might sleep)
* within interrupt context (simply because there is no use case for
* that yet).
* *
* Returns 0 on success, or an appropriate error code on failure * Returns 0 on success, or an appropriate error code on failure
*/ */
@ -513,7 +508,7 @@ int hwspin_lock_free(struct hwspinlock *hwlock)
return -EINVAL; return -EINVAL;
} }
spin_lock(&hwspinlock_tree_lock); mutex_lock(&hwspinlock_tree_lock);
/* make sure the hwspinlock is used */ /* make sure the hwspinlock is used */
ret = radix_tree_tag_get(&hwspinlock_tree, hwlock->id, 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); module_put(hwlock->dev->driver->owner);
out: out:
spin_unlock(&hwspinlock_tree_lock); mutex_unlock(&hwspinlock_tree_lock);
return ret; return ret;
} }
EXPORT_SYMBOL_GPL(hwspin_lock_free); EXPORT_SYMBOL_GPL(hwspin_lock_free);