From 93b465c2e186d96fb90012ba0f9372eb9952e732 Mon Sep 17 00:00:00 2001 From: Juan Gutierrez Date: Tue, 6 Sep 2011 09:30:16 +0300 Subject: 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: Signed-off-by: Juan Gutierrez [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 --- drivers/hwspinlock/hwspinlock_core.c | 45 ++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 25 deletions(-) (limited to 'drivers/hwspinlock') diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c index 4eb85b4a320e..0d20b82df0a7 100644 --- a/drivers/hwspinlock/hwspinlock_core.c +++ b/drivers/hwspinlock/hwspinlock_core.c @@ -26,6 +26,7 @@ #include #include #include +#include #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); -- cgit v1.2.3-59-g8ed1b