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Merge branch 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

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* 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (33 commits)
  lockdep: fix deadlock in lockdep_trace_alloc
  lockdep: annotate reclaim context (__GFP_NOFS), fix SLOB
  lockdep: annotate reclaim context (__GFP_NOFS), fix
  lockdep: build fix for !PROVE_LOCKING
  lockstat: warn about disabled lock debugging
  lockdep: use stringify.h
  lockdep: simplify check_prev_add_irq()
  lockdep: get_user_chars() redo
  lockdep: simplify get_user_chars()
  lockdep: add comments to mark_lock_irq()
  lockdep: remove macro usage from mark_held_locks()
  lockdep: fully reduce mark_lock_irq()
  lockdep: merge the !_READ mark_lock_irq() helpers
  lockdep: merge the _READ mark_lock_irq() helpers
  lockdep: simplify mark_lock_irq() helpers #3
  lockdep: further simplify mark_lock_irq() helpers
  lockdep: simplify the mark_lock_irq() helpers
  lockdep: split up mark_lock_irq()
  lockdep: generate usage strings
  lockdep: generate the state bit definitions
  ...
This commit is contained in:
Linus Torvalds
2009-03-30 17:17:35 -07:00
parent cf2f7d7c90 2f85018152
commit c4e1aa67ed
21 changed files with 731 additions and 380 deletions
Download Patch File Download Diff File Expand all files Collapse all files

530
kernel/lockdep.c
View File

@@ -41,6 +41,7 @@
#include <linux/utsname.h>
#include <linux/hash.h>
#include <linux/ftrace.h>
#include <linux/stringify.h>
#include <asm/sections.h>
@@ -310,12 +311,14 @@ EXPORT_SYMBOL(lockdep_on);
#if VERBOSE
# define HARDIRQ_VERBOSE 1
# define SOFTIRQ_VERBOSE 1
# define RECLAIM_VERBOSE 1
#else
# define HARDIRQ_VERBOSE 0
# define SOFTIRQ_VERBOSE 0
# define RECLAIM_VERBOSE 0
#endif
#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
/*
* Quick filtering for interesting events:
*/
@@ -443,17 +446,18 @@ atomic_t nr_find_usage_backwards_recursions;
* Locking printouts:
*/
#define __USAGE(__STATE) \
[LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
[LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
[LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
[LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
static const char *usage_str[] =
{
[LOCK_USED] = "initial-use ",
[LOCK_USED_IN_HARDIRQ] = "in-hardirq-W",
[LOCK_USED_IN_SOFTIRQ] = "in-softirq-W",
[LOCK_ENABLED_SOFTIRQS] = "softirq-on-W",
[LOCK_ENABLED_HARDIRQS] = "hardirq-on-W",
[LOCK_USED_IN_HARDIRQ_READ] = "in-hardirq-R",
[LOCK_USED_IN_SOFTIRQ_READ] = "in-softirq-R",
[LOCK_ENABLED_SOFTIRQS_READ] = "softirq-on-R",
[LOCK_ENABLED_HARDIRQS_READ] = "hardirq-on-R",
#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
#include "lockdep_states.h"
#undef LOCKDEP_STATE
[LOCK_USED] = "INITIAL USE",
};
const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
@@ -461,46 +465,45 @@ const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
}
void
get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4)
static inline unsigned long lock_flag(enum lock_usage_bit bit)
{
*c1 = '.', *c2 = '.', *c3 = '.', *c4 = '.';
return 1UL << bit;
}
if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
*c1 = '+';
else
if (class->usage_mask & LOCKF_ENABLED_HARDIRQS)
*c1 = '-';
static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
{
char c = '.';
if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
*c2 = '+';
else
if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS)
*c2 = '-';
if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
*c3 = '-';
if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ) {
*c3 = '+';
if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
*c3 = '?';
if (class->usage_mask & lock_flag(bit + 2))
c = '+';
if (class->usage_mask & lock_flag(bit)) {
c = '-';
if (class->usage_mask & lock_flag(bit + 2))
c = '?';
}
if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
*c4 = '-';
if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ) {
*c4 = '+';
if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
*c4 = '?';
}
return c;
}
void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
{
int i = 0;
#define LOCKDEP_STATE(__STATE) \
usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
#include "lockdep_states.h"
#undef LOCKDEP_STATE
usage[i] = '\0';
}
static void print_lock_name(struct lock_class *class)
{
char str[KSYM_NAME_LEN], c1, c2, c3, c4;
char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
const char *name;
get_usage_chars(class, &c1, &c2, &c3, &c4);
get_usage_chars(class, usage);
name = class->name;
if (!name) {
@@ -513,7 +516,7 @@ static void print_lock_name(struct lock_class *class)
if (class->subclass)
printk("/%d", class->subclass);
}
printk("){%c%c%c%c}", c1, c2, c3, c4);
printk("){%s}", usage);
}
static void print_lockdep_cache(struct lockdep_map *lock)
@@ -1263,9 +1266,49 @@ check_usage(struct task_struct *curr, struct held_lock *prev,
bit_backwards, bit_forwards, irqclass);
}
static int
check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next)
static const char *state_names[] = {
#define LOCKDEP_STATE(__STATE) \
__stringify(__STATE),
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
static const char *state_rnames[] = {
#define LOCKDEP_STATE(__STATE) \
__stringify(__STATE)"-READ",
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
static inline const char *state_name(enum lock_usage_bit bit)
{
return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
}
static int exclusive_bit(int new_bit)
{
/*
* USED_IN
* USED_IN_READ
* ENABLED
* ENABLED_READ
*
* bit 0 - write/read
* bit 1 - used_in/enabled
* bit 2+ state
*/
int state = new_bit & ~3;
int dir = new_bit & 2;
/*
* keep state, bit flip the direction and strip read.
*/
return state | (dir ^ 2);
}
static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next, enum lock_usage_bit bit)
{
/*
* Prove that the new dependency does not connect a hardirq-safe
@@ -1273,38 +1316,34 @@ check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
* the backwards-subgraph starting at <prev>, and the
* forwards-subgraph starting at <next>:
*/
if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ,
LOCK_ENABLED_HARDIRQS, "hard"))
if (!check_usage(curr, prev, next, bit,
exclusive_bit(bit), state_name(bit)))
return 0;
bit++; /* _READ */
/*
* Prove that the new dependency does not connect a hardirq-safe-read
* lock with a hardirq-unsafe lock - to achieve this we search
* the backwards-subgraph starting at <prev>, and the
* forwards-subgraph starting at <next>:
*/
if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ_READ,
LOCK_ENABLED_HARDIRQS, "hard-read"))
if (!check_usage(curr, prev, next, bit,
exclusive_bit(bit), state_name(bit)))
return 0;
/*
* Prove that the new dependency does not connect a softirq-safe
* lock with a softirq-unsafe lock - to achieve this we search
* the backwards-subgraph starting at <prev>, and the
* forwards-subgraph starting at <next>:
*/
if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ,
LOCK_ENABLED_SOFTIRQS, "soft"))
return 0;
/*
* Prove that the new dependency does not connect a softirq-safe-read
* lock with a softirq-unsafe lock - to achieve this we search
* the backwards-subgraph starting at <prev>, and the
* forwards-subgraph starting at <next>:
*/
if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ_READ,
LOCK_ENABLED_SOFTIRQS, "soft"))
return 1;
}
static int
check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next)
{
#define LOCKDEP_STATE(__STATE) \
if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
return 0;
#include "lockdep_states.h"
#undef LOCKDEP_STATE
return 1;
}
@@ -1933,7 +1972,7 @@ void print_irqtrace_events(struct task_struct *curr)
print_ip_sym(curr->softirq_disable_ip);
}
static int hardirq_verbose(struct lock_class *class)
static int HARDIRQ_verbose(struct lock_class *class)
{
#if HARDIRQ_VERBOSE
return class_filter(class);
@@ -1941,7 +1980,7 @@ static int hardirq_verbose(struct lock_class *class)
return 0;
}
static int softirq_verbose(struct lock_class *class)
static int SOFTIRQ_verbose(struct lock_class *class)
{
#if SOFTIRQ_VERBOSE
return class_filter(class);
@@ -1949,185 +1988,94 @@ static int softirq_verbose(struct lock_class *class)
return 0;
}
static int RECLAIM_FS_verbose(struct lock_class *class)
{
#if RECLAIM_VERBOSE
return class_filter(class);
#endif
return 0;
}
#define STRICT_READ_CHECKS 1
static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit)
{
int ret = 1;
static int (*state_verbose_f[])(struct lock_class *class) = {
#define LOCKDEP_STATE(__STATE) \
__STATE##_verbose,
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
switch(new_bit) {
case LOCK_USED_IN_HARDIRQ:
if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
static inline int state_verbose(enum lock_usage_bit bit,
struct lock_class *class)
{
return state_verbose_f[bit >> 2](class);
}
typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
enum lock_usage_bit bit, const char *name);
static int
mark_lock_irq(struct task_struct *curr, struct held_lock *this, int new_bit)
{
int excl_bit = exclusive_bit(new_bit);
int read = new_bit & 1;
int dir = new_bit & 2;
/*
* mark USED_IN has to look forwards -- to ensure no dependency
* has ENABLED state, which would allow recursion deadlocks.
*
* mark ENABLED has to look backwards -- to ensure no dependee
* has USED_IN state, which, again, would allow recursion deadlocks.
*/
check_usage_f usage = dir ?
check_usage_backwards : check_usage_forwards;
/*
* Validate that this particular lock does not have conflicting
* usage states.
*/
if (!valid_state(curr, this, new_bit, excl_bit))
return 0;
/*
* Validate that the lock dependencies don't have conflicting usage
* states.
*/
if ((!read || !dir || STRICT_READ_CHECKS) &&
!usage(curr, this, excl_bit, state_name(new_bit)))
return 0;
/*
* Check for read in write conflicts
*/
if (!read) {
if (!valid_state(curr, this, new_bit, excl_bit + 1))
return 0;
if (!valid_state(curr, this, new_bit,
LOCK_ENABLED_HARDIRQS_READ))
if (STRICT_READ_CHECKS &&
!usage(curr, this, excl_bit + 1,
state_name(new_bit + 1)))
return 0;
/*
* just marked it hardirq-safe, check that this lock
* took no hardirq-unsafe lock in the past:
*/
if (!check_usage_forwards(curr, this,
LOCK_ENABLED_HARDIRQS, "hard"))
return 0;
#if STRICT_READ_CHECKS
/*
* just marked it hardirq-safe, check that this lock
* took no hardirq-unsafe-read lock in the past:
*/
if (!check_usage_forwards(curr, this,
LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
return 0;
#endif
if (hardirq_verbose(hlock_class(this)))
ret = 2;
break;
case LOCK_USED_IN_SOFTIRQ:
if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
return 0;
if (!valid_state(curr, this, new_bit,
LOCK_ENABLED_SOFTIRQS_READ))
return 0;
/*
* just marked it softirq-safe, check that this lock
* took no softirq-unsafe lock in the past:
*/
if (!check_usage_forwards(curr, this,
LOCK_ENABLED_SOFTIRQS, "soft"))
return 0;
#if STRICT_READ_CHECKS
/*
* just marked it softirq-safe, check that this lock
* took no softirq-unsafe-read lock in the past:
*/
if (!check_usage_forwards(curr, this,
LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
return 0;
#endif
if (softirq_verbose(hlock_class(this)))
ret = 2;
break;
case LOCK_USED_IN_HARDIRQ_READ:
if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
return 0;
/*
* just marked it hardirq-read-safe, check that this lock
* took no hardirq-unsafe lock in the past:
*/
if (!check_usage_forwards(curr, this,
LOCK_ENABLED_HARDIRQS, "hard"))
return 0;
if (hardirq_verbose(hlock_class(this)))
ret = 2;
break;
case LOCK_USED_IN_SOFTIRQ_READ:
if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
return 0;
/*
* just marked it softirq-read-safe, check that this lock
* took no softirq-unsafe lock in the past:
*/
if (!check_usage_forwards(curr, this,
LOCK_ENABLED_SOFTIRQS, "soft"))
return 0;
if (softirq_verbose(hlock_class(this)))
ret = 2;
break;
case LOCK_ENABLED_HARDIRQS:
if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
return 0;
if (!valid_state(curr, this, new_bit,
LOCK_USED_IN_HARDIRQ_READ))
return 0;
/*
* just marked it hardirq-unsafe, check that no hardirq-safe
* lock in the system ever took it in the past:
*/
if (!check_usage_backwards(curr, this,
LOCK_USED_IN_HARDIRQ, "hard"))
return 0;
#if STRICT_READ_CHECKS
/*
* just marked it hardirq-unsafe, check that no
* hardirq-safe-read lock in the system ever took
* it in the past:
*/
if (!check_usage_backwards(curr, this,
LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
return 0;
#endif
if (hardirq_verbose(hlock_class(this)))
ret = 2;
break;
case LOCK_ENABLED_SOFTIRQS:
if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
return 0;
if (!valid_state(curr, this, new_bit,
LOCK_USED_IN_SOFTIRQ_READ))
return 0;
/*
* just marked it softirq-unsafe, check that no softirq-safe
* lock in the system ever took it in the past:
*/
if (!check_usage_backwards(curr, this,
LOCK_USED_IN_SOFTIRQ, "soft"))
return 0;
#if STRICT_READ_CHECKS
/*
* just marked it softirq-unsafe, check that no
* softirq-safe-read lock in the system ever took
* it in the past:
*/
if (!check_usage_backwards(curr, this,
LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
return 0;
#endif
if (softirq_verbose(hlock_class(this)))
ret = 2;
break;
case LOCK_ENABLED_HARDIRQS_READ:
if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
return 0;
#if STRICT_READ_CHECKS
/*
* just marked it hardirq-read-unsafe, check that no
* hardirq-safe lock in the system ever took it in the past:
*/
if (!check_usage_backwards(curr, this,
LOCK_USED_IN_HARDIRQ, "hard"))
return 0;
#endif
if (hardirq_verbose(hlock_class(this)))
ret = 2;
break;
case LOCK_ENABLED_SOFTIRQS_READ:
if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
return 0;
#if STRICT_READ_CHECKS
/*
* just marked it softirq-read-unsafe, check that no
* softirq-safe lock in the system ever took it in the past:
*/
if (!check_usage_backwards(curr, this,
LOCK_USED_IN_SOFTIRQ, "soft"))
return 0;
#endif
if (softirq_verbose(hlock_class(this)))
ret = 2;
break;
default:
WARN_ON(1);
break;
}
return ret;
if (state_verbose(new_bit, hlock_class(this)))
return 2;
return 1;
}
enum mark_type {
#define LOCKDEP_STATE(__STATE) __STATE,
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
/*
* Mark all held locks with a usage bit:
*/
static int
mark_held_locks(struct task_struct *curr, int hardirq)
mark_held_locks(struct task_struct *curr, enum mark_type mark)
{
enum lock_usage_bit usage_bit;
struct held_lock *hlock;
@@ -2136,17 +2084,12 @@ mark_held_locks(struct task_struct *curr, int hardirq)
for (i = 0; i < curr->lockdep_depth; i++) {
hlock = curr->held_locks + i;
if (hardirq) {
if (hlock->read)
usage_bit = LOCK_ENABLED_HARDIRQS_READ;
else
usage_bit = LOCK_ENABLED_HARDIRQS;
} else {
if (hlock->read)
usage_bit = LOCK_ENABLED_SOFTIRQS_READ;
else
usage_bit = LOCK_ENABLED_SOFTIRQS;
}
usage_bit = 2 + (mark << 2); /* ENABLED */
if (hlock->read)
usage_bit += 1; /* READ */
BUG_ON(usage_bit >= LOCK_USAGE_STATES);
if (!mark_lock(curr, hlock, usage_bit))
return 0;
}
@@ -2200,7 +2143,7 @@ void trace_hardirqs_on_caller(unsigned long ip)
* We are going to turn hardirqs on, so set the
* usage bit for all held locks:
*/
if (!mark_held_locks(curr, 1))
if (!mark_held_locks(curr, HARDIRQ))
return;
/*
* If we have softirqs enabled, then set the usage
@@ -2208,7 +2151,7 @@ void trace_hardirqs_on_caller(unsigned long ip)
* this bit from being set before)
*/
if (curr->softirqs_enabled)
if (!mark_held_locks(curr, 0))
if (!mark_held_locks(curr, SOFTIRQ))
return;
curr->hardirq_enable_ip = ip;
@@ -2288,7 +2231,7 @@ void trace_softirqs_on(unsigned long ip)
* enabled too:
*/
if (curr->hardirqs_enabled)
mark_held_locks(curr, 0);
mark_held_locks(curr, SOFTIRQ);
}
/*
@@ -2317,6 +2260,48 @@ void trace_softirqs_off(unsigned long ip)
debug_atomic_inc(&redundant_softirqs_off);
}
static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
{
struct task_struct *curr = current;
if (unlikely(!debug_locks))
return;
/* no reclaim without waiting on it */
if (!(gfp_mask & __GFP_WAIT))
return;
/* this guy won't enter reclaim */
if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
return;
/* We're only interested __GFP_FS allocations for now */
if (!(gfp_mask & __GFP_FS))
return;
if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
return;
mark_held_locks(curr, RECLAIM_FS);
}
static void check_flags(unsigned long flags);
void lockdep_trace_alloc(gfp_t gfp_mask)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion = 1;
__lockdep_trace_alloc(gfp_mask, flags);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}
static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
{
/*
@@ -2345,19 +2330,35 @@ static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
if (!hlock->hardirqs_off) {
if (hlock->read) {
if (!mark_lock(curr, hlock,
LOCK_ENABLED_HARDIRQS_READ))
LOCK_ENABLED_HARDIRQ_READ))
return 0;
if (curr->softirqs_enabled)
if (!mark_lock(curr, hlock,
LOCK_ENABLED_SOFTIRQS_READ))
LOCK_ENABLED_SOFTIRQ_READ))
return 0;
} else {
if (!mark_lock(curr, hlock,
LOCK_ENABLED_HARDIRQS))
LOCK_ENABLED_HARDIRQ))
return 0;
if (curr->softirqs_enabled)
if (!mark_lock(curr, hlock,
LOCK_ENABLED_SOFTIRQS))
LOCK_ENABLED_SOFTIRQ))
return 0;
}
}
/*
* We reuse the irq context infrastructure more broadly as a general
* context checking code. This tests GFP_FS recursion (a lock taken
* during reclaim for a GFP_FS allocation is held over a GFP_FS
* allocation).
*/
if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
if (hlock->read) {
if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
return 0;
} else {
if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
return 0;
}
}
@@ -2412,6 +2413,10 @@ static inline int separate_irq_context(struct task_struct *curr,
return 0;
}
void lockdep_trace_alloc(gfp_t gfp_mask)
{
}
#endif
/*
@@ -2445,14 +2450,13 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
return 0;
switch (new_bit) {
case LOCK_USED_IN_HARDIRQ:
case LOCK_USED_IN_SOFTIRQ:
case LOCK_USED_IN_HARDIRQ_READ:
case LOCK_USED_IN_SOFTIRQ_READ:
case LOCK_ENABLED_HARDIRQS:
case LOCK_ENABLED_SOFTIRQS:
case LOCK_ENABLED_HARDIRQS_READ:
case LOCK_ENABLED_SOFTIRQS_READ:
#define LOCKDEP_STATE(__STATE) \
case LOCK_USED_IN_##__STATE: \
case LOCK_USED_IN_##__STATE##_READ: \
case LOCK_ENABLED_##__STATE: \
case LOCK_ENABLED_##__STATE##_READ:
#include "lockdep_states.h"
#undef LOCKDEP_STATE
ret = mark_lock_irq(curr, this, new_bit);
if (!ret)
return 0;
@@ -2966,6 +2970,16 @@ void lock_release(struct lockdep_map *lock, int nested,
}
EXPORT_SYMBOL_GPL(lock_release);
void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
{
current->lockdep_reclaim_gfp = gfp_mask;
}
void lockdep_clear_current_reclaim_state(void)
{
current->lockdep_reclaim_gfp = 0;
}
#ifdef CONFIG_LOCK_STAT
static int
print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,

45
kernel/lockdep_internals.h
View File

@@ -6,6 +6,45 @@
* lockdep subsystem internal functions and variables.
*/
/*
* Lock-class usage-state bits:
*/
enum lock_usage_bit {
#define LOCKDEP_STATE(__STATE) \
LOCK_USED_IN_##__STATE, \
LOCK_USED_IN_##__STATE##_READ, \
LOCK_ENABLED_##__STATE, \
LOCK_ENABLED_##__STATE##_READ,
#include "lockdep_states.h"
#undef LOCKDEP_STATE
LOCK_USED,
LOCK_USAGE_STATES
};
/*
* Usage-state bitmasks:
*/
#define __LOCKF(__STATE) LOCKF_##__STATE = (1 << LOCK_##__STATE),
enum {
#define LOCKDEP_STATE(__STATE) \
__LOCKF(USED_IN_##__STATE) \
__LOCKF(USED_IN_##__STATE##_READ) \
__LOCKF(ENABLED_##__STATE) \
__LOCKF(ENABLED_##__STATE##_READ)
#include "lockdep_states.h"
#undef LOCKDEP_STATE
__LOCKF(USED)
};
#define LOCKF_ENABLED_IRQ (LOCKF_ENABLED_HARDIRQ | LOCKF_ENABLED_SOFTIRQ)
#define LOCKF_USED_IN_IRQ (LOCKF_USED_IN_HARDIRQ | LOCKF_USED_IN_SOFTIRQ)
#define LOCKF_ENABLED_IRQ_READ \
(LOCKF_ENABLED_HARDIRQ_READ | LOCKF_ENABLED_SOFTIRQ_READ)
#define LOCKF_USED_IN_IRQ_READ \
(LOCKF_USED_IN_HARDIRQ_READ | LOCKF_USED_IN_SOFTIRQ_READ)
/*
* MAX_LOCKDEP_ENTRIES is the maximum number of lock dependencies
* we track.
@@ -31,8 +70,10 @@
extern struct list_head all_lock_classes;
extern struct lock_chain lock_chains[];
extern void
get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4);
#define LOCK_USAGE_CHARS (1+LOCK_USAGE_STATES/2)
extern void get_usage_chars(struct lock_class *class,
char usage[LOCK_USAGE_CHARS]);
extern const char * __get_key_name(struct lockdep_subclass_key *key, char *str);

22
kernel/lockdep_proc.c
View File

@@ -84,7 +84,7 @@ static int l_show(struct seq_file *m, void *v)
{
struct lock_class *class = v;
struct lock_list *entry;
char c1, c2, c3, c4;
char usage[LOCK_USAGE_CHARS];
if (v == SEQ_START_TOKEN) {
seq_printf(m, "all lock classes:\n");
@@ -100,8 +100,8 @@ static int l_show(struct seq_file *m, void *v)
seq_printf(m, " BD:%5ld", lockdep_count_backward_deps(class));
#endif
get_usage_chars(class, &c1, &c2, &c3, &c4);
seq_printf(m, " %c%c%c%c", c1, c2, c3, c4);
get_usage_chars(class, usage);
seq_printf(m, " %s", usage);
seq_printf(m, ": ");
print_name(m, class);
@@ -300,27 +300,27 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
nr_uncategorized++;
if (class->usage_mask & LOCKF_USED_IN_IRQ)
nr_irq_safe++;
if (class->usage_mask & LOCKF_ENABLED_IRQS)
if (class->usage_mask & LOCKF_ENABLED_IRQ)
nr_irq_unsafe++;
if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
nr_softirq_safe++;
if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS)
if (class->usage_mask & LOCKF_ENABLED_SOFTIRQ)
nr_softirq_unsafe++;
if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
nr_hardirq_safe++;
if (class->usage_mask & LOCKF_ENABLED_HARDIRQS)
if (class->usage_mask & LOCKF_ENABLED_HARDIRQ)
nr_hardirq_unsafe++;
if (class->usage_mask & LOCKF_USED_IN_IRQ_READ)
nr_irq_read_safe++;
if (class->usage_mask & LOCKF_ENABLED_IRQS_READ)
if (class->usage_mask & LOCKF_ENABLED_IRQ_READ)
nr_irq_read_unsafe++;
if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ)
nr_softirq_read_safe++;
if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
if (class->usage_mask & LOCKF_ENABLED_SOFTIRQ_READ)
nr_softirq_read_unsafe++;
if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ)
nr_hardirq_read_safe++;
if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
if (class->usage_mask & LOCKF_ENABLED_HARDIRQ_READ)
nr_hardirq_read_unsafe++;
#ifdef CONFIG_PROVE_LOCKING
@@ -601,6 +601,10 @@ static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
static void seq_header(struct seq_file *m)
{
seq_printf(m, "lock_stat version 0.3\n");
if (unlikely(!debug_locks))
seq_printf(m, "*WARNING* lock debugging disabled!! - possibly due to a lockdep warning\n");
seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));
seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s "
"%14s %14s\n",

9
kernel/lockdep_states.h Normal file
View File

@@ -0,0 +1,9 @@
/*
* Lockdep states,
*
* please update XXX_LOCK_USAGE_STATES in include/linux/lockdep.h whenever
* you add one, or come up with a nice dynamic solution.
*/
LOCKDEP_STATE(HARDIRQ)
LOCKDEP_STATE(SOFTIRQ)
LOCKDEP_STATE(RECLAIM_FS)

9
kernel/mutex-debug.c
View File

@@ -26,11 +26,6 @@
/*
* Must be called with lock->wait_lock held.
*/
void debug_mutex_set_owner(struct mutex *lock, struct thread_info *new_owner)
{
lock->owner = new_owner;
}
void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)
{
memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter));
@@ -59,7 +54,6 @@ void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
/* 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,
@@ -82,7 +76,7 @@ void debug_mutex_unlock(struct mutex *lock)
DEBUG_LOCKS_WARN_ON(lock->magic != lock);
DEBUG_LOCKS_WARN_ON(lock->owner != current_thread_info());
DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
DEBUG_LOCKS_WARN_ON(lock->owner != current_thread_info());
mutex_clear_owner(lock);
}
void debug_mutex_init(struct mutex *lock, const char *name,
@@ -95,7 +89,6 @@ void debug_mutex_init(struct mutex *lock, const char *name,
debug_check_no_locks_freed((void *)lock, sizeof(*lock));
lockdep_init_map(&lock->dep_map, name, key, 0);
#endif
lock->owner = NULL;
lock->magic = lock;
}

18
kernel/mutex-debug.h
View File

@@ -13,14 +13,6 @@
/*
* This must be called with lock->wait_lock held.
*/
extern void
debug_mutex_set_owner(struct mutex *lock, struct thread_info *new_owner);
static inline void debug_mutex_clear_owner(struct mutex *lock)
{
lock->owner = NULL;
}
extern void debug_mutex_lock_common(struct mutex *lock,
struct mutex_waiter *waiter);
extern void debug_mutex_wake_waiter(struct mutex *lock,
@@ -35,6 +27,16 @@ extern void debug_mutex_unlock(struct mutex *lock);
extern void debug_mutex_init(struct mutex *lock, const char *name,
struct lock_class_key *key);
static inline void mutex_set_owner(struct mutex *lock)
{
lock->owner = current_thread_info();
}
static inline void mutex_clear_owner(struct mutex *lock)
{
lock->owner = NULL;
}
#define spin_lock_mutex(lock, flags) \
do { \
struct mutex *l = container_of(lock, struct mutex, wait_lock); \

121
kernel/mutex.c
View File

@@ -10,6 +10,11 @@
* Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
* David Howells for suggestions and improvements.
*
* - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
* from the -rt tree, where it was originally implemented for rtmutexes
* by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
* and Sven Dietrich.
*
* Also see Documentation/mutex-design.txt.
*/
#include <linux/mutex.h>
@@ -46,6 +51,7 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
atomic_set(&lock->count, 1);
spin_lock_init(&lock->wait_lock);
INIT_LIST_HEAD(&lock->wait_list);
mutex_clear_owner(lock);
debug_mutex_init(lock, name, key);
}
@@ -91,6 +97,7 @@ void inline __sched mutex_lock(struct mutex *lock)
* 'unlocked' into 'locked' state.
*/
__mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath);
mutex_set_owner(lock);
}
EXPORT_SYMBOL(mutex_lock);
@@ -115,6 +122,14 @@ void __sched mutex_unlock(struct mutex *lock)
* The unlocking fastpath is the 0->1 transition from 'locked'
* into 'unlocked' state:
*/
#ifndef CONFIG_DEBUG_MUTEXES
/*
* When debugging is enabled we must not clear the owner before time,
* the slow path will always be taken, and that clears the owner field
* after verifying that it was indeed current.
*/
mutex_clear_owner(lock);
#endif
__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);
}
@@ -129,21 +144,75 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
{
struct task_struct *task = current;
struct mutex_waiter waiter;
unsigned int old_val;
unsigned long flags;
preempt_disable();
mutex_acquire(&lock->dep_map, subclass, 0, ip);
#if defined(CONFIG_SMP) && !defined(CONFIG_DEBUG_MUTEXES)
/*
* Optimistic spinning.
*
* We try to spin for acquisition when we find that there are no
* pending waiters and the lock owner is currently running on a
* (different) CPU.
*
* The rationale is that if the lock owner is running, it is likely to
* release the lock soon.
*
* Since this needs the lock owner, and this mutex implementation
* doesn't track the owner atomically in the lock field, we need to
* track it non-atomically.
*
* We can't do this for DEBUG_MUTEXES because that relies on wait_lock
* to serialize everything.
*/
for (;;) {
struct thread_info *owner;
/*
* If there's an owner, wait for it to either
* release the lock or go to sleep.
*/
owner = ACCESS_ONCE(lock->owner);
if (owner && !mutex_spin_on_owner(lock, owner))
break;
if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
lock_acquired(&lock->dep_map, ip);
mutex_set_owner(lock);
preempt_enable();
return 0;
}
/*
* When there's no owner, we might have preempted between the
* owner acquiring the lock and setting the owner field. If
* we're an RT task that will live-lock because we won't let
* the owner complete.
*/
if (!owner && (need_resched() || rt_task(task)))
break;
/*
* The cpu_relax() call is a compiler barrier which forces
* everything in this loop to be re-loaded. We don't need
* memory barriers as we'll eventually observe the right
* values at the cost of a few extra spins.
*/
cpu_relax();
}
#endif
spin_lock_mutex(&lock->wait_lock, flags);
debug_mutex_lock_common(lock, &waiter);
mutex_acquire(&lock->dep_map, subclass, 0, ip);
debug_mutex_add_waiter(lock, &waiter, task_thread_info(task));
/* add waiting tasks to the end of the waitqueue (FIFO): */
list_add_tail(&waiter.list, &lock->wait_list);
waiter.task = task;
old_val = atomic_xchg(&lock->count, -1);
if (old_val == 1)
if (atomic_xchg(&lock->count, -1) == 1)
goto done;
lock_contended(&lock->dep_map, ip);
@@ -158,8 +227,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
* that when we release the lock, we properly wake up the
* other waiters:
*/
old_val = atomic_xchg(&lock->count, -1);
if (old_val == 1)
if (atomic_xchg(&lock->count, -1) == 1)
break;
/*
@@ -173,21 +241,22 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
spin_unlock_mutex(&lock->wait_lock, flags);
debug_mutex_free_waiter(&waiter);
preempt_enable();
return -EINTR;
}
__set_task_state(task, state);
/* didnt get the lock, go to sleep: */
spin_unlock_mutex(&lock->wait_lock, flags);
schedule();
__schedule();
spin_lock_mutex(&lock->wait_lock, flags);
}
done:
lock_acquired(&lock->dep_map, ip);
/* got the lock - rejoice! */
mutex_remove_waiter(lock, &waiter, task_thread_info(task));
debug_mutex_set_owner(lock, task_thread_info(task));
mutex_remove_waiter(lock, &waiter, current_thread_info());
mutex_set_owner(lock);
/* set it to 0 if there are no waiters left: */
if (likely(list_empty(&lock->wait_list)))
@@ -196,6 +265,7 @@ done:
spin_unlock_mutex(&lock->wait_lock, flags);
debug_mutex_free_waiter(&waiter);
preempt_enable();
return 0;
}
@@ -222,7 +292,8 @@ int __sched
mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
{
might_sleep();
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass, _RET_IP_);
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
subclass, _RET_IP_);
}
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
@@ -260,8 +331,6 @@ __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
wake_up_process(waiter->task);
}
debug_mutex_clear_owner(lock);
spin_unlock_mutex(&lock->wait_lock, flags);
}
@@ -298,18 +367,30 @@ __mutex_lock_interruptible_slowpath(atomic_t *lock_count);
*/
int __sched mutex_lock_interruptible(struct mutex *lock)
{
int ret;
might_sleep();
return __mutex_fastpath_lock_retval
ret = __mutex_fastpath_lock_retval
(&lock->count, __mutex_lock_interruptible_slowpath);
if (!ret)
mutex_set_owner(lock);
return ret;
}
EXPORT_SYMBOL(mutex_lock_interruptible);
int __sched mutex_lock_killable(struct mutex *lock)
{
int ret;
might_sleep();
return __mutex_fastpath_lock_retval
ret = __mutex_fastpath_lock_retval
(&lock->count, __mutex_lock_killable_slowpath);
if (!ret)
mutex_set_owner(lock);
return ret;
}
EXPORT_SYMBOL(mutex_lock_killable);
@@ -352,9 +433,10 @@ static inline int __mutex_trylock_slowpath(atomic_t *lock_count)
prev = atomic_xchg(&lock->count, -1);
if (likely(prev == 1)) {
debug_mutex_set_owner(lock, current_thread_info());
mutex_set_owner(lock);
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
}
/* Set it back to 0 if there are no waiters: */
if (likely(list_empty(&lock->wait_list)))
atomic_set(&lock->count, 0);
@@ -380,8 +462,13 @@ static inline int __mutex_trylock_slowpath(atomic_t *lock_count)
*/
int __sched mutex_trylock(struct mutex *lock)
{
return __mutex_fastpath_trylock(&lock->count,
__mutex_trylock_slowpath);
int ret;
ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath);
if (ret)
mutex_set_owner(lock);
return ret;
}
EXPORT_SYMBOL(mutex_trylock);

22
kernel/mutex.h
View File

@@ -16,8 +16,26 @@
#define mutex_remove_waiter(lock, waiter, ti) \
__list_del((waiter)->list.prev, (waiter)->list.next)
#define debug_mutex_set_owner(lock, new_owner) do { } while (0)
#define debug_mutex_clear_owner(lock) do { } while (0)
#ifdef CONFIG_SMP
static inline void mutex_set_owner(struct mutex *lock)
{
lock->owner = current_thread_info();
}
static inline void mutex_clear_owner(struct mutex *lock)
{
lock->owner = NULL;
}
#else
static inline void mutex_set_owner(struct mutex *lock)
{
}
static inline void mutex_clear_owner(struct mutex *lock)
{
}
#endif
#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) do { } while (0)

71
kernel/sched.c
View File

@@ -4942,15 +4942,13 @@ pick_next_task(struct rq *rq)
/*
* schedule() is the main scheduler function.
*/
asmlinkage void __sched schedule(void)
asmlinkage void __sched __schedule(void)
{
struct task_struct *prev, *next;
unsigned long *switch_count;
struct rq *rq;
int cpu;
need_resched:
preempt_disable();
cpu = smp_processor_id();
rq = cpu_rq(cpu);
rcu_qsctr_inc(cpu);
@@ -5007,13 +5005,80 @@ need_resched_nonpreemptible:
if (unlikely(reacquire_kernel_lock(current) < 0))
goto need_resched_nonpreemptible;
}
asmlinkage void __sched schedule(void)
{
need_resched:
preempt_disable();
__schedule();
preempt_enable_no_resched();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
EXPORT_SYMBOL(schedule);
#ifdef CONFIG_SMP
/*
* Look out! "owner" is an entirely speculative pointer
* access and not reliable.
*/
int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
{
unsigned int cpu;
struct rq *rq;
if (!sched_feat(OWNER_SPIN))
return 0;
#ifdef CONFIG_DEBUG_PAGEALLOC
/*
* Need to access the cpu field knowing that
* DEBUG_PAGEALLOC could have unmapped it if
* the mutex owner just released it and exited.
*/
if (probe_kernel_address(&owner->cpu, cpu))
goto out;
#else
cpu = owner->cpu;
#endif
/*
* Even if the access succeeded (likely case),
* the cpu field may no longer be valid.
*/
if (cpu >= nr_cpumask_bits)
goto out;
/*
* We need to validate that we can do a
* get_cpu() and that we have the percpu area.
*/
if (!cpu_online(cpu))
goto out;
rq = cpu_rq(cpu);
for (;;) {
/*
* Owner changed, break to re-assess state.
*/
if (lock->owner != owner)
break;
/*
* Is that owner really running on that cpu?
*/
if (task_thread_info(rq->curr) != owner || need_resched())
return 0;
cpu_relax();
}
out:
return 1;
}
#endif
#ifdef CONFIG_PREEMPT
/*
* this is the entry point to schedule() from in-kernel preemption

1
kernel/sched_features.h
View File

@@ -14,3 +14,4 @@ SCHED_FEAT(LB_WAKEUP_UPDATE, 1)
SCHED_FEAT(ASYM_EFF_LOAD, 1)
SCHED_FEAT(WAKEUP_OVERLAP, 0)
SCHED_FEAT(LAST_BUDDY, 1)
SCHED_FEAT(OWNER_SPIN, 1)

68
kernel/timer.c
View File

@@ -491,14 +491,18 @@ static inline void debug_timer_free(struct timer_list *timer)
debug_object_free(timer, &timer_debug_descr);
}
static void __init_timer(struct timer_list *timer);
static void __init_timer(struct timer_list *timer,
const char *name,
struct lock_class_key *key);
void init_timer_on_stack(struct timer_list *timer)
void init_timer_on_stack_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
debug_object_init_on_stack(timer, &timer_debug_descr);
__init_timer(timer);
__init_timer(timer, name, key);
}
EXPORT_SYMBOL_GPL(init_timer_on_stack);
EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
void destroy_timer_on_stack(struct timer_list *timer)
{
@@ -512,7 +516,9 @@ static inline void debug_timer_activate(struct timer_list *timer) { }
static inline void debug_timer_deactivate(struct timer_list *timer) { }
#endif
static void __init_timer(struct timer_list *timer)
static void __init_timer(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
timer->entry.next = NULL;
timer->base = __raw_get_cpu_var(tvec_bases);
@@ -521,6 +527,7 @@ static void __init_timer(struct timer_list *timer)
timer->start_pid = -1;
memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
lockdep_init_map(&timer->lockdep_map, name, key, 0);
}
/**
@@ -530,19 +537,23 @@ static void __init_timer(struct timer_list *timer)
* init_timer() must be done to a timer prior calling *any* of the
* other timer functions.
*/
void init_timer(struct timer_list *timer)
void init_timer_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
debug_timer_init(timer);
__init_timer(timer);
__init_timer(timer, name, key);
}
EXPORT_SYMBOL(init_timer);
EXPORT_SYMBOL(init_timer_key);
void init_timer_deferrable(struct timer_list *timer)
void init_timer_deferrable_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
init_timer(timer);
init_timer_key(timer, name, key);
timer_set_deferrable(timer);
}
EXPORT_SYMBOL(init_timer_deferrable);
EXPORT_SYMBOL(init_timer_deferrable_key);
static inline void detach_timer(struct timer_list *timer,
int clear_pending)
@@ -826,6 +837,15 @@ EXPORT_SYMBOL(try_to_del_timer_sync);
*/
int del_timer_sync(struct timer_list *timer)
{
#ifdef CONFIG_LOCKDEP
unsigned long flags;
local_irq_save(flags);
lock_map_acquire(&timer->lockdep_map);
lock_map_release(&timer->lockdep_map);
local_irq_restore(flags);
#endif
for (;;) {
int ret = try_to_del_timer_sync(timer);
if (ret >= 0)
@@ -897,10 +917,36 @@ static inline void __run_timers(struct tvec_base *base)
set_running_timer(base, timer);
detach_timer(timer, 1);
spin_unlock_irq(&base->lock);
{
int preempt_count = preempt_count();
#ifdef CONFIG_LOCKDEP
/*
* It is permissible to free the timer from
* inside the function that is called from
* it, this we need to take into account for
* lockdep too. To avoid bogus "held lock
* freed" warnings as well as problems when
* looking into timer->lockdep_map, make a
* copy and use that here.
*/
struct lockdep_map lockdep_map =
timer->lockdep_map;
#endif
/*
* Couple the lock chain with the lock chain at
* del_timer_sync() by acquiring the lock_map
* around the fn() call here and in
* del_timer_sync().
*/
lock_map_acquire(&lockdep_map);
fn(data);
lock_map_release(&lockdep_map);
if (preempt_count != preempt_count()) {
printk(KERN_ERR "huh, entered %p "
"with preempt_count %08x, exited"