diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/Makefile | 3 | ||||
| -rw-r--r-- | kernel/cpuset.c | 10 | ||||
| -rw-r--r-- | kernel/exit.c | 5 | ||||
| -rw-r--r-- | kernel/fork.c | 4 | ||||
| -rw-r--r-- | kernel/mutex-debug.c | 464 | ||||
| -rw-r--r-- | kernel/mutex-debug.h | 134 | ||||
| -rw-r--r-- | kernel/mutex.c | 325 | ||||
| -rw-r--r-- | kernel/mutex.h | 35 | ||||
| -rw-r--r-- | kernel/sched.c | 1 |
9 files changed, 975 insertions, 6 deletions
diff --git a/kernel/Makefile b/kernel/Makefile index 4f5a1453093a..a940bac02837 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -7,8 +7,9 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \ sysctl.o capability.o ptrace.o timer.o user.o \ signal.o sys.o kmod.o workqueue.o pid.o \ rcupdate.o intermodule.o extable.o params.o posix-timers.o \ - kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o + kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o +obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o obj-$(CONFIG_FUTEX) += futex.o obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o obj-$(CONFIG_SMP) += cpu.o spinlock.o diff --git a/kernel/cpuset.c b/kernel/cpuset.c index eab64e23bcae..2a75e44e1a41 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1513,7 +1513,7 @@ static int cpuset_add_file(struct dentry *dir, const struct cftype *cft) struct dentry *dentry; int error; - down(&dir->d_inode->i_sem); + mutex_lock(&dir->d_inode->i_mutex); dentry = cpuset_get_dentry(dir, cft->name); if (!IS_ERR(dentry)) { error = cpuset_create_file(dentry, 0644 | S_IFREG); @@ -1522,7 +1522,7 @@ static int cpuset_add_file(struct dentry *dir, const struct cftype *cft) dput(dentry); } else error = PTR_ERR(dentry); - up(&dir->d_inode->i_sem); + mutex_unlock(&dir->d_inode->i_mutex); return error; } @@ -1793,7 +1793,7 @@ static long cpuset_create(struct cpuset *parent, const char *name, int mode) /* * Release manage_sem before cpuset_populate_dir() because it - * will down() this new directory's i_sem and if we race with + * will down() this new directory's i_mutex and if we race with * another mkdir, we might deadlock. */ up(&manage_sem); @@ -1812,7 +1812,7 @@ static int cpuset_mkdir(struct inode *dir, struct dentry *dentry, int mode) { struct cpuset *c_parent = dentry->d_parent->d_fsdata; - /* the vfs holds inode->i_sem already */ + /* the vfs holds inode->i_mutex already */ return cpuset_create(c_parent, dentry->d_name.name, mode | S_IFDIR); } @@ -1823,7 +1823,7 @@ static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry) struct cpuset *parent; char *pathbuf = NULL; - /* the vfs holds both inode->i_sem already */ + /* the vfs holds both inode->i_mutex already */ down(&manage_sem); cpuset_update_task_memory_state(); diff --git a/kernel/exit.c b/kernel/exit.c index caceabf3f230..309a46fa16f8 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -29,6 +29,7 @@ #include <linux/syscalls.h> #include <linux/signal.h> #include <linux/cn_proc.h> +#include <linux/mutex.h> #include <asm/uaccess.h> #include <asm/unistd.h> @@ -869,6 +870,10 @@ fastcall NORET_TYPE void do_exit(long code) mpol_free(tsk->mempolicy); tsk->mempolicy = NULL; #endif + /* + * If DEBUG_MUTEXES is on, make sure we are holding no locks: + */ + mutex_debug_check_no_locks_held(tsk); /* PF_DEAD causes final put_task_struct after we schedule. */ preempt_disable(); diff --git a/kernel/fork.c b/kernel/fork.c index 72e3252c6763..b18d64554feb 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -979,6 +979,10 @@ static task_t *copy_process(unsigned long clone_flags, } #endif +#ifdef CONFIG_DEBUG_MUTEXES + p->blocked_on = NULL; /* not blocked yet */ +#endif + p->tgid = p->pid; if (clone_flags & CLONE_THREAD) p->tgid = current->tgid; diff --git a/kernel/mutex-debug.c b/kernel/mutex-debug.c new file mode 100644 index 000000000000..4fcb051a8b9e --- /dev/null +++ b/kernel/mutex-debug.c @@ -0,0 +1,464 @@ +/* + * kernel/mutex-debug.c + * + * Debugging code for mutexes + * + * Started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> + * + * lock debugging, locking tree, deadlock detection started by: + * + * Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey + * Released under the General Public License (GPL). + */ +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/delay.h> +#include <linux/module.h> +#include <linux/spinlock.h> +#include <linux/kallsyms.h> +#include <linux/interrupt.h> + +#include <asm/mutex.h> + +#include "mutex-debug.h" + +/* + * We need a global lock when we walk through the multi-process + * lock tree. Only used in the deadlock-debugging case. + */ +DEFINE_SPINLOCK(debug_mutex_lock); + +/* + * All locks held by all tasks, in a single global list: + */ +LIST_HEAD(debug_mutex_held_locks); + +/* + * In the debug case we carry the caller's instruction pointer into + * other functions, but we dont want the function argument overhead + * in the nondebug case - hence these macros: + */ +#define __IP_DECL__ , unsigned long ip +#define __IP__ , ip +#define __RET_IP__ , (unsigned long)__builtin_return_address(0) + +/* + * "mutex debugging enabled" flag. We turn it off when we detect + * the first problem because we dont want to recurse back + * into the tracing code when doing error printk or + * executing a BUG(): + */ +int debug_mutex_on = 1; + +static void printk_task(struct task_struct *p) +{ + if (p) + printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio); + else + printk("<none>"); +} + +static void printk_ti(struct thread_info *ti) +{ + if (ti) + printk_task(ti->task); + else + printk("<none>"); +} + +static void printk_task_short(struct task_struct *p) +{ + if (p) + printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio); + else + printk("<none>"); +} + +static void printk_lock(struct mutex *lock, int print_owner) +{ + printk(" [%p] {%s}\n", lock, lock->name); + + if (print_owner && lock->owner) { + printk(".. held by: "); + printk_ti(lock->owner); + printk("\n"); + } + if (lock->owner) { + printk("... acquired at: "); + print_symbol("%s\n", lock->acquire_ip); + } +} + +/* + * printk locks held by a task: + */ +static void show_task_locks(struct task_struct *p) +{ + switch (p->state) { + case TASK_RUNNING: printk("R"); break; + case TASK_INTERRUPTIBLE: printk("S"); break; + case TASK_UNINTERRUPTIBLE: printk("D"); break; + case TASK_STOPPED: printk("T"); break; + case EXIT_ZOMBIE: printk("Z"); break; + case EXIT_DEAD: printk("X"); break; + default: printk("?"); break; + } + printk_task(p); + if (p->blocked_on) { + struct mutex *lock = p->blocked_on->lock; + + printk(" blocked on mutex:"); + printk_lock(lock, 1); + } else + printk(" (not blocked on mutex)\n"); +} + +/* + * printk all locks held in the system (if filter == NULL), + * or all locks belonging to a single task (if filter != NULL): + */ +void show_held_locks(struct task_struct *filter) +{ + struct list_head *curr, *cursor = NULL; + struct mutex *lock; + struct thread_info *t; + unsigned long flags; + int count = 0; + + if (filter) { + printk("------------------------------\n"); + printk("| showing all locks held by: | ("); + printk_task_short(filter); + printk("):\n"); + printk("------------------------------\n"); + } else { + printk("---------------------------\n"); + printk("| showing all locks held: |\n"); + printk("---------------------------\n"); + } + + /* + * Play safe and acquire the global trace lock. We + * cannot printk with that lock held so we iterate + * very carefully: + */ +next: + debug_spin_lock_save(&debug_mutex_lock, flags); + list_for_each(curr, &debug_mutex_held_locks) { + if (cursor && curr != cursor) + continue; + lock = list_entry(curr, struct mutex, held_list); + t = lock->owner; + if (filter && (t != filter->thread_info)) + continue; + count++; + cursor = curr->next; + debug_spin_lock_restore(&debug_mutex_lock, flags); + + printk("\n#%03d: ", count); + printk_lock(lock, filter ? 0 : 1); + goto next; + } + debug_spin_lock_restore(&debug_mutex_lock, flags); + printk("\n"); +} + +void mutex_debug_show_all_locks(void) +{ + struct task_struct *g, *p; + int count = 10; + int unlock = 1; + + printk("\nShowing all blocking locks in the system:\n"); + + /* + * Here we try to get the tasklist_lock as hard as possible, + * if not successful after 2 seconds we ignore it (but keep + * trying). This is to enable a debug printout even if a + * tasklist_lock-holding task deadlocks or crashes. + */ +retry: + if (!read_trylock(&tasklist_lock)) { + if (count == 10) + printk("hm, tasklist_lock locked, retrying... "); + if (count) { + count--; + printk(" #%d", 10-count); + mdelay(200); + goto retry; + } + printk(" ignoring it.\n"); + unlock = 0; + } + if (count != 10) + printk(" locked it.\n"); + + do_each_thread(g, p) { + show_task_locks(p); + if (!unlock) + if (read_trylock(&tasklist_lock)) + unlock = 1; + } while_each_thread(g, p); + + printk("\n"); + show_held_locks(NULL); + printk("=============================================\n\n"); + + if (unlock) + read_unlock(&tasklist_lock); +} + +static void report_deadlock(struct task_struct *task, struct mutex *lock, + struct mutex *lockblk, unsigned long ip) +{ + printk("\n%s/%d is trying to acquire this lock:\n", + current->comm, current->pid); + printk_lock(lock, 1); + printk("... trying at: "); + print_symbol("%s\n", ip); + show_held_locks(current); + + if (lockblk) { + printk("but %s/%d is deadlocking current task %s/%d!\n\n", + task->comm, task->pid, current->comm, current->pid); + printk("\n%s/%d is blocked on this lock:\n", + task->comm, task->pid); + printk_lock(lockblk, 1); + + show_held_locks(task); + + printk("\n%s/%d's [blocked] stackdump:\n\n", + task->comm, task->pid); + show_stack(task, NULL); + } + + printk("\n%s/%d's [current] stackdump:\n\n", + current->comm, current->pid); + dump_stack(); + mutex_debug_show_all_locks(); + printk("[ turning off deadlock detection. Please report this. ]\n\n"); + local_irq_disable(); +} + +/* + * Recursively check for mutex deadlocks: + */ +static int check_deadlock(struct mutex *lock, int depth, + struct thread_info *ti, unsigned long ip) +{ + struct mutex *lockblk; + struct task_struct *task; + + if (!debug_mutex_on) + return 0; + + ti = lock->owner; + if (!ti) + return 0; + + task = ti->task; + lockblk = NULL; + if (task->blocked_on) + lockblk = task->blocked_on->lock; + + /* Self-deadlock: */ + if (current == task) { + DEBUG_OFF(); + if (depth) + return 1; + printk("\n==========================================\n"); + printk( "[ BUG: lock recursion deadlock detected! |\n"); + printk( "------------------------------------------\n"); + report_deadlock(task, lock, NULL, ip); + return 0; + } + + /* Ugh, something corrupted the lock data structure? */ + if (depth > 20) { + DEBUG_OFF(); + printk("\n===========================================\n"); + printk( "[ BUG: infinite lock dependency detected!? |\n"); + printk( "-------------------------------------------\n"); + report_deadlock(task, lock, lockblk, ip); + return 0; + } + + /* Recursively check for dependencies: */ + if (lockblk && check_deadlock(lockblk, depth+1, ti, ip)) { + printk("\n============================================\n"); + printk( "[ BUG: circular locking deadlock detected! ]\n"); + printk( "--------------------------------------------\n"); + report_deadlock(task, lock, lockblk, ip); + return 0; + } + return 0; +} + +/* + * Called when a task exits, this function checks whether the + * task is holding any locks, and reports the first one if so: + */ +void mutex_debug_check_no_locks_held(struct task_struct *task) +{ + struct list_head *curr, *next; + struct thread_info *t; + unsigned long flags; + struct mutex *lock; + + if (!debug_mutex_on) + return; + + debug_spin_lock_save(&debug_mutex_lock, flags); + list_for_each_safe(curr, next, &debug_mutex_held_locks) { + lock = list_entry(curr, struct mutex, held_list); + t = lock->owner; + if (t != task->thread_info) + continue; + list_del_init(curr); + DEBUG_OFF(); + debug_spin_lock_restore(&debug_mutex_lock, flags); + + printk("BUG: %s/%d, lock held at task exit time!\n", + task->comm, task->pid); + printk_lock(lock, 1); + if (lock->owner != task->thread_info) + printk("exiting task is not even the owner??\n"); + return; + } + debug_spin_lock_restore(&debug_mutex_lock, flags); +} + +/* + * Called when kernel memory is freed (or unmapped), or if a mutex + * is destroyed or reinitialized - this code checks whether there is + * any held lock in the memory range of <from> to <to>: + */ +void mutex_debug_check_no_locks_freed(const void *from, const void *to) +{ + struct list_head *curr, *next; + unsigned long flags; + struct mutex *lock; + void *lock_addr; + + if (!debug_mutex_on) + return; + + debug_spin_lock_save(&debug_mutex_lock, flags); + list_for_each_safe(curr, next, &debug_mutex_held_locks) { + lock = list_entry(curr, struct mutex, held_list); + lock_addr = lock; + if (lock_addr < from || lock_addr >= to) + continue; + list_del_init(curr); + DEBUG_OFF(); + debug_spin_lock_restore(&debug_mutex_lock, flags); + + printk("BUG: %s/%d, active lock [%p(%p-%p)] freed!\n", + current->comm, current->pid, lock, from, to); + dump_stack(); + printk_lock(lock, 1); + if (lock->owner != current_thread_info()) + printk("freeing task is not even the owner??\n"); + return; + } + debug_spin_lock_restore(&debug_mutex_lock, flags); +} + +/* + * Must be called with lock->wait_lock held. + */ +void debug_mutex_set_owner(struct mutex *lock, + struct thread_info *new_owner __IP_DECL__) +{ + lock->owner = new_owner; + DEBUG_WARN_ON(!list_empty(&lock->held_list)); + if (debug_mutex_on) { + list_add_tail(&lock->held_list, &debug_mutex_held_locks); + lock->acquire_ip = ip; + } +} + +void debug_mutex_init_waiter(struct mutex_waiter *waiter) +{ + memset(waiter, 0x11, sizeof(*waiter)); + waiter->magic = waiter; + INIT_LIST_HEAD(&waiter->list); +} + +void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter) +{ + SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock)); + DEBUG_WARN_ON(list_empty(&lock->wait_list)); + DEBUG_WARN_ON(waiter->magic != waiter); + DEBUG_WARN_ON(list_empty(&waiter->list)); +} + +void debug_mutex_free_waiter(struct mutex_waiter *waiter) +{ + DEBUG_WARN_ON(!list_empty(&waiter->list)); + memset(waiter, 0x22, sizeof(*waiter)); +} + +void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti __IP_DECL__) +{ + SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock)); + check_deadlock(lock, 0, ti, ip); + /* Mark the current thread as blocked on the lock: */ + ti->task->blocked_on = waiter; + waiter->lock = lock; +} + +void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti) +{ + DEBUG_WARN_ON(list_empty(&waiter->list)); + DEBUG_WARN_ON(waiter->task != ti->task); + DEBUG_WARN_ON(ti->task->blocked_on != waiter); + ti->task->blocked_on = NULL; + + list_del_init(&waiter->list); + waiter->task = NULL; +} + +void debug_mutex_unlock(struct mutex *lock) +{ + DEBUG_WARN_ON(lock->magic != lock); + DEBUG_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next); + DEBUG_WARN_ON(lock->owner != current_thread_info()); + if (debug_mutex_on) { + DEBUG_WARN_ON(list_empty(&lock->held_list)); + list_del_init(&lock->held_list); + } +} + +void debug_mutex_init(struct mutex *lock, const char *name) +{ + /* + * Make sure we are not reinitializing a held lock: + */ + mutex_debug_check_no_locks_freed((void *)lock, (void *)(lock + 1)); + lock->owner = NULL; + INIT_LIST_HEAD(&lock->held_list); + lock->name = name; + lock->magic = lock; +} + +/*** + * mutex_destroy - mark a mutex unusable + * @lock: the mutex to be destroyed + * + * This function marks the mutex uninitialized, and any subsequent + * use of the mutex is forbidden. The mutex must not be locked when + * this function is called. + */ +void fastcall mutex_destroy(struct mutex *lock) +{ + DEBUG_WARN_ON(mutex_is_locked(lock)); + lock->magic = NULL; +} + +EXPORT_SYMBOL_GPL(mutex_destroy); + diff --git a/kernel/mutex-debug.h b/kernel/mutex-debug.h new file mode 100644 index 000000000000..fd384050acb1 --- /dev/null +++ b/kernel/mutex-debug.h @@ -0,0 +1,134 @@ +/* + * Mutexes: blocking mutual exclusion locks + * + * started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> + * + * This file contains mutex debugging related internal declarations, + * prototypes and inline functions, for the CONFIG_DEBUG_MUTEXES case. + * More details are in kernel/mutex-debug.c. + */ + +extern spinlock_t debug_mutex_lock; +extern struct list_head debug_mutex_held_locks; +extern int debug_mutex_on; + +/* + * In the debug case we carry the caller's instruction pointer into + * other functions, but we dont want the function argument overhead + * in the nondebug case - hence these macros: + */ +#define __IP_DECL__ , unsigned long ip +#define __IP__ , ip +#define __RET_IP__ , (unsigned long)__builtin_return_address(0) + +/* + * This must be called with lock->wait_lock held. + */ +extern void debug_mutex_set_owner(struct mutex *lock, + struct thread_info *new_owner __IP_DECL__); + +static inline void debug_mutex_clear_owner(struct mutex *lock) +{ + lock->owner = NULL; +} + +extern void debug_mutex_init_waiter(struct mutex_waiter *waiter); +extern void debug_mutex_wake_waiter(struct mutex *lock, + struct mutex_waiter *waiter); +extern void debug_mutex_free_waiter(struct mutex_waiter *waiter); +extern void debug_mutex_add_waiter(struct mutex *lock, + struct mutex_waiter *waiter, + struct thread_info *ti __IP_DECL__); +extern void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti); +extern void debug_mutex_unlock(struct mutex *lock); +extern void debug_mutex_init(struct mutex *lock, const char *name); + +#define debug_spin_lock(lock) \ + do { \ + local_irq_disable(); \ + if (debug_mutex_on) \ + spin_lock(lock); \ + } while (0) + +#define debug_spin_unlock(lock) \ + do { \ + if (debug_mutex_on) \ + spin_unlock(lock); \ + local_irq_enable(); \ + preempt_check_resched(); \ + } while (0) + +#define debug_spin_lock_save(lock, flags) \ + do { \ + local_irq_save(flags); \ + if (debug_mutex_on) \ + spin_lock(lock); \ + } while (0) + +#define debug_spin_lock_restore(lock, flags) \ + do { \ + if (debug_mutex_on) \ + spin_unlock(lock); \ + local_irq_restore(flags); \ + preempt_check_resched(); \ + } while (0) + +#define spin_lock_mutex(lock) \ + do { \ + struct mutex *l = container_of(lock, struct mutex, wait_lock); \ + \ + DEBUG_WARN_ON(in_interrupt()); \ + debug_spin_lock(&debug_mutex_lock); \ + spin_lock(lock); \ + DEBUG_WARN_ON(l->magic != l); \ + } while (0) + +#define spin_unlock_mutex(lock) \ + do { \ + spin_unlock(lock); \ + debug_spin_unlock(&debug_mutex_lock); \ + } while (0) + +#define DEBUG_OFF() \ +do { \ + if (debug_mutex_on) { \ + debug_mutex_on = 0; \ + console_verbose(); \ + if (spin_is_locked(&debug_mutex_lock)) \ + spin_unlock(&debug_mutex_lock); \ + } \ +} while (0) + +#define DEBUG_BUG() \ +do { \ + if (debug_mutex_on) { \ + DEBUG_OFF(); \ + BUG(); \ + } \ +} while (0) + +#define DEBUG_WARN_ON(c) \ +do { \ + if (unlikely(c && debug_mutex_on)) { \ + DEBUG_OFF(); \ + WARN_ON(1); \ + } \ +} while (0) + +# define DEBUG_BUG_ON(c) \ +do { \ + if (unlikely(c)) \ + DEBUG_BUG(); \ +} while (0) + +#ifdef CONFIG_SMP +# define SMP_DEBUG_WARN_ON(c) DEBUG_WARN_ON(c) +# define SMP_DEBUG_BUG_ON(c) DEBUG_BUG_ON(c) +#else +# define SMP_DEBUG_WARN_ON(c) do { } while (0) +# define SMP_DEBUG_BUG_ON(c) do { } while (0) +#endif + diff --git a/kernel/mutex.c b/kernel/mutex.c new file mode 100644 index 000000000000..7eb960661441 --- /dev/null +++ b/kernel/mutex.c @@ -0,0 +1,325 @@ +/* + * kernel/mutex.c + * + * Mutexes: blocking mutual exclusion locks + * + * Started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> + * + * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and + * David Howells for suggestions and improvements. + * + * Also see Documentation/mutex-design.txt. + */ +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/module.h> +#include <linux/spinlock.h> +#include <linux/interrupt.h> + +/* + * In the DEBUG case we are using the "NULL fastpath" for mutexes, + * which forces all calls into the slowpath: + */ +#ifdef CONFIG_DEBUG_MUTEXES +# include "mutex-debug.h" +# include <asm-generic/mutex-null.h> +#else +# include "mutex.h" +# include <asm/mutex.h> +#endif + +/*** + * mutex_init - initialize the mutex + * @lock: the mutex to be initialized + * + * Initialize the mutex to unlocked state. + * + * It is not allowed to initialize an already locked mutex. + */ +void fastcall __mutex_init(struct mutex *lock, const char *name) +{ + atomic_set(&lock->count, 1); + spin_lock_init(&lock->wait_lock); + INIT_LIST_HEAD(&lock->wait_list); + + debug_mutex_init(lock, name); +} + +EXPORT_SYMBOL(__mutex_init); + +/* + * We split the mutex lock/unlock logic into separate fastpath and + * slowpath functions, to reduce the register pressure on the fastpath. + * We also put the fastpath first in the kernel image, to make sure the + * branch is predicted by the CPU as default-untaken. + */ +static void fastcall noinline __sched +__mutex_lock_slowpath(atomic_t *lock_count __IP_DECL__); + +/*** + * mutex_lock - acquire the mutex + * @lock: the mutex to be acquired + * + * Lock the mutex exclusively for this task. If the mutex is not + * available right now, it will sleep until it can get it. + * + * The mutex must later on be released by the same task that + * acquired it. Recursive locking is not allowed. The task + * may not exit without first unlocking the mutex. Also, kernel + * memory where the mutex resides mutex must not be freed with + * the mutex still locked. The mutex must first be initialized + * (or statically defined) before it can be locked. memset()-ing + * the mutex to 0 is not allowed. + * + * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging + * checks that will enforce the restrictions and will also do + * deadlock debugging. ) + * + * This function is similar to (but not equivalent to) down(). + */ +void fastcall __sched mutex_lock(struct mutex *lock) +{ + /* + * The locking fastpath is the 1->0 transition from + * 'unlocked' into 'locked' state. + * + * NOTE: if asm/mutex.h is included, then some architectures + * rely on mutex_lock() having _no other code_ here but this + * fastpath. That allows the assembly fastpath to do + * tail-merging optimizations. (If you want to put testcode + * here, do it under #ifndef CONFIG_MUTEX_DEBUG.) + */ + __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); +} + +EXPORT_SYMBOL(mutex_lock); + +static void fastcall noinline __sched +__mutex_unlock_slowpath(atomic_t *lock_count __IP_DECL__); + +/*** + * mutex_unlock - release the mutex + * @lock: the mutex to be released + * + * Unlock a mutex that has been locked by this task previously. + * + * This function must not be used in interrupt context. Unlocking + * of a not locked mutex is not allowed. + * + * This function is similar to (but not equivalent to) up(). + */ +void fastcall __sched mutex_unlock(struct mutex *lock) +{ + /* + * The unlocking fastpath is the 0->1 transition from 'locked' + * into 'unlocked' state: + * + * NOTE: no other code must be here - see mutex_lock() . + */ + __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); +} + +EXPORT_SYMBOL(mutex_unlock); + +/* + * Lock a mutex (possibly interruptible), slowpath: + */ +static inline int __sched +__mutex_lock_common(struct mutex *lock, long state __IP_DECL__) +{ + struct task_struct *task = current; + struct mutex_waiter waiter; + unsigned int old_val; + + debug_mutex_init_waiter(&waiter); + + spin_lock_mutex(&lock->wait_lock); + + debug_mutex_add_waiter(lock, &waiter, task->thread_info, ip); + + /* add waiting tasks to the end of the waitqueue (FIFO): */ + list_add_tail(&waiter.list, &lock->wait_list); + waiter.task = task; + + for (;;) { + /* + * Lets try to take the lock again - this is needed even if + * we get here for the first time (shortly after failing to + * acquire the lock), to make sure that we get a wakeup once + * it's unlocked. Later on, if we sleep, this is the + * operation that gives us the lock. We xchg it to -1, so + * that when we release the lock, we properly wake up the + * other waiters: + */ + old_val = atomic_xchg(&lock->count, -1); + if (old_val == 1) + break; + + /* + * got a signal? (This code gets eliminated in the + * TASK_UNINTERRUPTIBLE case.) + */ + if (unlikely(state == TASK_INTERRUPTIBLE && + signal_pending(task))) { + mutex_remove_waiter(lock, &waiter, task->thread_info); + spin_unlock_mutex(&lock->wait_lock); + + debug_mutex_free_waiter(&waiter); + return -EINTR; + } + __set_task_state(task, state); + + /* didnt get the lock, go to sleep: */ + spin_unlock_mutex(&lock->wait_lock); + schedule(); + spin_lock_mutex(&lock->wait_lock); + } + + /* got the lock - rejoice! */ + mutex_remove_waiter(lock, &waiter, task->thread_info); + debug_mutex_set_owner(lock, task->thread_info __IP__); + + /* set it to 0 if there are no waiters left: */ + if (likely(list_empty(&lock->wait_list))) + atomic_set(&lock->count, 0); + + spin_unlock_mutex(&lock->wait_lock); + + debug_mutex_free_waiter(&waiter); + + DEBUG_WARN_ON(list_empty(&lock->held_list)); + DEBUG_WARN_ON(lock->owner != task->thread_info); + + return 0; +} + +static void fastcall noinline __sched +__mutex_lock_slowpath(atomic_t *lock_count __IP_DECL__) +{ + struct mutex *lock = container_of(lock_count, struct mutex, count); + + __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE __IP__); +} + +/* + * Release the lock, slowpath: + */ +static fastcall noinline void +__mutex_unlock_slowpath(atomic_t *lock_count __IP_DECL__) +{ + struct mutex *lock = container_of(lock_count, struct mutex, count); + + DEBUG_WARN_ON(lock->owner != current_thread_info()); + + spin_lock_mutex(&lock->wait_lock); + + /* + * some architectures leave the lock unlocked in the fastpath failure + * case, others need to leave it locked. In the later case we have to + * unlock it here + */ + if (__mutex_slowpath_needs_to_unlock()) + atomic_set(&lock->count, 1); + + debug_mutex_unlock(lock); + + if (!list_empty(&lock->wait_list)) { + /* get the first entry from the wait-list: */ + struct mutex_waiter *waiter = + list_entry(lock->wait_list.next, + struct mutex_waiter, list); + + debug_mutex_wake_waiter(lock, waiter); + + wake_up_process(waiter->task); + } + + debug_mutex_clear_owner(lock); + + spin_unlock_mutex(&lock->wait_lock); +} + +/* + * Here come the less common (and hence less performance-critical) APIs: + * mutex_lock_interruptible() and mutex_trylock(). + */ +static int fastcall noinline __sched +__mutex_lock_interruptible_slowpath(atomic_t *lock_count __IP_DECL__); + +/*** + * mutex_lock_interruptible - acquire the mutex, interruptable + * @lock: the mutex to be acquired + * + * Lock the mutex like mutex_lock(), and return 0 if the mutex has + * been acquired or sleep until the mutex becomes available. If a + * signal arrives while waiting for the lock then this function + * returns -EINTR. + * + * This function is similar to (but not equivalent to) down_interruptible(). + */ +int fastcall __sched mutex_lock_interruptible(struct mutex *lock) +{ + /* NOTE: no other code must be here - see mutex_lock() */ + return __mutex_fastpath_lock_retval + (&lock->count, __mutex_lock_interruptible_slowpath); +} + +EXPORT_SYMBOL(mutex_lock_interruptible); + +static int fastcall noinline __sched +__mutex_lock_interruptible_slowpath(atomic_t *lock_count __IP_DECL__) +{ + struct mutex *lock = container_of(lock_count, struct mutex, count); + + return __mutex_lock_common(lock, TASK_INTERRUPTIBLE __IP__); +} + +/* + * Spinlock based trylock, we take the spinlock and check whether we + * can get the lock: + */ +static inline int __mutex_trylock_slowpath(atomic_t *lock_count) +{ + struct mutex *lock = container_of(lock_count, struct mutex, count); + int prev; + + spin_lock_mutex(&lock->wait_lock); + + prev = atomic_xchg(&lock->count, -1); + if (likely(prev == 1)) + debug_mutex_set_owner(lock, current_thread_info() __RET_IP__); + /* Set it back to 0 if there are no waiters: */ + if (likely(list_empty(&lock->wait_list))) + atomic_set(&lock->count, 0); + + spin_unlock_mutex(&lock->wait_lock); + + return prev == 1; +} + +/*** + * mutex_trylock - try acquire the mutex, without waiting + * @lock: the mutex to be acquired + * + * Try to acquire the mutex atomically. Returns 1 if the mutex + * has been acquired successfully, and 0 on contention. + * + * NOTE: this function follows the spin_trylock() convention, so + * it is negated to the down_trylock() return values! Be careful + * about this when converting semaphore users to mutexes. + * + * This function must not be used in interrupt context. The + * mutex must be released by the same task that acquired it. + */ +int fastcall mutex_trylock(struct mutex *lock) +{ + return __mutex_fastpath_trylock(&lock->count, + __mutex_trylock_slowpath); +} + +EXPORT_SYMBOL(mutex_trylock); + + + diff --git a/kernel/mutex.h b/kernel/mutex.h new file mode 100644 index 000000000000..00fe84e7b672 --- /dev/null +++ b/kernel/mutex.h @@ -0,0 +1,35 @@ +/* + * Mutexes: blocking mutual exclusion locks + * + * started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> + * + * This file contains mutex debugging related internal prototypes, for the + * !CONFIG_DEBUG_MUTEXES case. Most of them are NOPs: + */ + +#define spin_lock_mutex(lock) spin_lock(lock) +#define spin_unlock_mutex(lock) spin_unlock(lock) +#define mutex_remove_waiter(lock, waiter, ti) \ + __list_del((waiter)->list.prev, (waiter)->list.next) + +#define DEBUG_WARN_ON(c) do { } while (0) +#define debug_mutex_set_owner(lock, new_owner) do { } while (0) +#define debug_mutex_clear_owner(lock) do { } while (0) +#define debug_mutex_init_waiter(waiter) do { } while (0) +#define debug_mutex_wake_waiter(lock, waiter) do { } while (0) +#define debug_mutex_free_waiter(waiter) do { } while (0) +#define debug_mutex_add_waiter(lock, waiter, ti, ip) do { } while (0) +#define debug_mutex_unlock(lock) do { } while (0) +#define debug_mutex_init(lock, name) do { } while (0) + +/* + * Return-address parameters/declarations. They are very useful for + * debugging, but add overhead in the !DEBUG case - so we go the + * trouble of using this not too elegant but zero-cost solution: + */ +#define __IP_DECL__ +#define __IP__ +#define __RET_IP__ + diff --git a/kernel/sched.c b/kernel/sched.c index 92733091154c..34a945bcc022 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4386,6 +4386,7 @@ void show_state(void) } while_each_thread(g, p); read_unlock(&tasklist_lock); + mutex_debug_show_all_locks(); } /** |