f20786ff4d
Introduce the core lock statistics code.
Lock statistics provides lock wait-time and hold-time (as well as the count
of corresponding contention and acquisitions events). Also, the first few
call-sites that encounter contention are tracked.
Lock wait-time is the time spent waiting on the lock. This provides insight
into the locking scheme, that is, a heavily contended lock is indicative of
a too coarse locking scheme.
Lock hold-time is the duration the lock was held, this provides a reference for
the wait-time numbers, so they can be put into perspective.
1)
lock
2)
... do stuff ..
unlock
3)
The time between 1 and 2 is the wait-time. The time between 2 and 3 is the
hold-time.
The lockdep held-lock tracking code is reused, because it already collects locks
into meaningful groups (classes), and because it is an existing infrastructure
for lock instrumentation.
Currently lockdep tracks lock acquisition with two hooks:
lock()
lock_acquire()
_lock()
... code protected by lock ...
unlock()
lock_release()
_unlock()
We need to extend this with two more hooks, in order to measure contention.
lock_contended() - used to measure contention events
lock_acquired() - completion of the contention
These are then placed the following way:
lock()
lock_acquire()
if (!_try_lock())
lock_contended()
_lock()
lock_acquired()
... do locked stuff ...
unlock()
lock_release()
_unlock()
(Note: the try_lock() 'trick' is used to avoid instrumenting all platform
dependent lock primitive implementations.)
It is also possible to toggle the two lockdep features at runtime using:
/proc/sys/kernel/prove_locking
/proc/sys/kernel/lock_stat
(esp. turning off the O(n^2) prove_locking functionaliy can help)
[akpm@linux-foundation.org: build fixes]
[akpm@linux-foundation.org: nuke unneeded ifdefs]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
428 lines
12 KiB
C
428 lines
12 KiB
C
/*
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* Runtime locking correctness validator
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*
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* Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* see Documentation/lockdep-design.txt for more details.
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*/
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#ifndef __LINUX_LOCKDEP_H
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#define __LINUX_LOCKDEP_H
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struct task_struct;
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struct lockdep_map;
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#ifdef CONFIG_LOCKDEP
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#include <linux/linkage.h>
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#include <linux/list.h>
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#include <linux/debug_locks.h>
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#include <linux/stacktrace.h>
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/*
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* Lock-class usage-state bits:
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*/
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enum lock_usage_bit
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{
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LOCK_USED = 0,
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LOCK_USED_IN_HARDIRQ,
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LOCK_USED_IN_SOFTIRQ,
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LOCK_ENABLED_SOFTIRQS,
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LOCK_ENABLED_HARDIRQS,
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LOCK_USED_IN_HARDIRQ_READ,
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LOCK_USED_IN_SOFTIRQ_READ,
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LOCK_ENABLED_SOFTIRQS_READ,
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LOCK_ENABLED_HARDIRQS_READ,
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LOCK_USAGE_STATES
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};
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/*
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* Usage-state bitmasks:
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*/
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#define LOCKF_USED (1 << LOCK_USED)
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#define LOCKF_USED_IN_HARDIRQ (1 << LOCK_USED_IN_HARDIRQ)
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#define LOCKF_USED_IN_SOFTIRQ (1 << LOCK_USED_IN_SOFTIRQ)
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#define LOCKF_ENABLED_HARDIRQS (1 << LOCK_ENABLED_HARDIRQS)
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#define LOCKF_ENABLED_SOFTIRQS (1 << LOCK_ENABLED_SOFTIRQS)
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#define LOCKF_ENABLED_IRQS (LOCKF_ENABLED_HARDIRQS | LOCKF_ENABLED_SOFTIRQS)
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#define LOCKF_USED_IN_IRQ (LOCKF_USED_IN_HARDIRQ | LOCKF_USED_IN_SOFTIRQ)
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#define LOCKF_USED_IN_HARDIRQ_READ (1 << LOCK_USED_IN_HARDIRQ_READ)
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#define LOCKF_USED_IN_SOFTIRQ_READ (1 << LOCK_USED_IN_SOFTIRQ_READ)
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#define LOCKF_ENABLED_HARDIRQS_READ (1 << LOCK_ENABLED_HARDIRQS_READ)
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#define LOCKF_ENABLED_SOFTIRQS_READ (1 << LOCK_ENABLED_SOFTIRQS_READ)
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#define LOCKF_ENABLED_IRQS_READ \
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(LOCKF_ENABLED_HARDIRQS_READ | LOCKF_ENABLED_SOFTIRQS_READ)
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#define LOCKF_USED_IN_IRQ_READ \
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(LOCKF_USED_IN_HARDIRQ_READ | LOCKF_USED_IN_SOFTIRQ_READ)
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#define MAX_LOCKDEP_SUBCLASSES 8UL
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/*
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* Lock-classes are keyed via unique addresses, by embedding the
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* lockclass-key into the kernel (or module) .data section. (For
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* static locks we use the lock address itself as the key.)
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*/
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struct lockdep_subclass_key {
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char __one_byte;
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} __attribute__ ((__packed__));
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struct lock_class_key {
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struct lockdep_subclass_key subkeys[MAX_LOCKDEP_SUBCLASSES];
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};
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/*
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* The lock-class itself:
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*/
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struct lock_class {
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/*
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* class-hash:
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*/
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struct list_head hash_entry;
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/*
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* global list of all lock-classes:
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*/
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struct list_head lock_entry;
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struct lockdep_subclass_key *key;
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unsigned int subclass;
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/*
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* IRQ/softirq usage tracking bits:
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*/
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unsigned long usage_mask;
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struct stack_trace usage_traces[LOCK_USAGE_STATES];
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/*
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* These fields represent a directed graph of lock dependencies,
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* to every node we attach a list of "forward" and a list of
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* "backward" graph nodes.
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*/
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struct list_head locks_after, locks_before;
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/*
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* Generation counter, when doing certain classes of graph walking,
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* to ensure that we check one node only once:
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*/
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unsigned int version;
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/*
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* Statistics counter:
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*/
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unsigned long ops;
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const char *name;
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int name_version;
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#ifdef CONFIG_LOCK_STAT
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unsigned long contention_point[4];
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#endif
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};
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#ifdef CONFIG_LOCK_STAT
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struct lock_time {
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s64 min;
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s64 max;
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s64 total;
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unsigned long nr;
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};
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struct lock_class_stats {
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unsigned long contention_point[4];
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struct lock_time read_waittime;
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struct lock_time write_waittime;
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struct lock_time read_holdtime;
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struct lock_time write_holdtime;
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};
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struct lock_class_stats lock_stats(struct lock_class *class);
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void clear_lock_stats(struct lock_class *class);
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#endif
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/*
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* Map the lock object (the lock instance) to the lock-class object.
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* This is embedded into specific lock instances:
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*/
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struct lockdep_map {
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struct lock_class_key *key;
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struct lock_class *class_cache;
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const char *name;
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};
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/*
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* Every lock has a list of other locks that were taken after it.
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* We only grow the list, never remove from it:
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*/
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struct lock_list {
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struct list_head entry;
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struct lock_class *class;
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struct stack_trace trace;
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int distance;
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};
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/*
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* We record lock dependency chains, so that we can cache them:
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*/
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struct lock_chain {
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struct list_head entry;
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u64 chain_key;
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};
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struct held_lock {
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/*
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* One-way hash of the dependency chain up to this point. We
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* hash the hashes step by step as the dependency chain grows.
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*
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* We use it for dependency-caching and we skip detection
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* passes and dependency-updates if there is a cache-hit, so
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* it is absolutely critical for 100% coverage of the validator
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* to have a unique key value for every unique dependency path
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* that can occur in the system, to make a unique hash value
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* as likely as possible - hence the 64-bit width.
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*
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* The task struct holds the current hash value (initialized
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* with zero), here we store the previous hash value:
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*/
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u64 prev_chain_key;
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struct lock_class *class;
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unsigned long acquire_ip;
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struct lockdep_map *instance;
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#ifdef CONFIG_LOCK_STAT
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u64 waittime_stamp;
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u64 holdtime_stamp;
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#endif
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/*
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* The lock-stack is unified in that the lock chains of interrupt
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* contexts nest ontop of process context chains, but we 'separate'
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* the hashes by starting with 0 if we cross into an interrupt
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* context, and we also keep do not add cross-context lock
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* dependencies - the lock usage graph walking covers that area
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* anyway, and we'd just unnecessarily increase the number of
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* dependencies otherwise. [Note: hardirq and softirq contexts
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* are separated from each other too.]
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*
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* The following field is used to detect when we cross into an
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* interrupt context:
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*/
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int irq_context;
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int trylock;
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int read;
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int check;
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int hardirqs_off;
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};
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/*
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* Initialization, self-test and debugging-output methods:
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*/
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extern void lockdep_init(void);
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extern void lockdep_info(void);
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extern void lockdep_reset(void);
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extern void lockdep_reset_lock(struct lockdep_map *lock);
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extern void lockdep_free_key_range(void *start, unsigned long size);
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extern void lockdep_off(void);
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extern void lockdep_on(void);
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/*
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* These methods are used by specific locking variants (spinlocks,
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* rwlocks, mutexes and rwsems) to pass init/acquire/release events
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* to lockdep:
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*/
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extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
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struct lock_class_key *key, int subclass);
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/*
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* Reinitialize a lock key - for cases where there is special locking or
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* special initialization of locks so that the validator gets the scope
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* of dependencies wrong: they are either too broad (they need a class-split)
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* or they are too narrow (they suffer from a false class-split):
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*/
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#define lockdep_set_class(lock, key) \
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lockdep_init_map(&(lock)->dep_map, #key, key, 0)
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#define lockdep_set_class_and_name(lock, key, name) \
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lockdep_init_map(&(lock)->dep_map, name, key, 0)
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#define lockdep_set_class_and_subclass(lock, key, sub) \
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lockdep_init_map(&(lock)->dep_map, #key, key, sub)
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#define lockdep_set_subclass(lock, sub) \
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lockdep_init_map(&(lock)->dep_map, #lock, \
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(lock)->dep_map.key, sub)
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/*
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* Acquire a lock.
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*
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* Values for "read":
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*
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* 0: exclusive (write) acquire
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* 1: read-acquire (no recursion allowed)
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* 2: read-acquire with same-instance recursion allowed
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*
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* Values for check:
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*
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* 0: disabled
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* 1: simple checks (freeing, held-at-exit-time, etc.)
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* 2: full validation
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*/
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extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
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int trylock, int read, int check, unsigned long ip);
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extern void lock_release(struct lockdep_map *lock, int nested,
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unsigned long ip);
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# define INIT_LOCKDEP .lockdep_recursion = 0,
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#define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
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#else /* !LOCKDEP */
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static inline void lockdep_off(void)
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{
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}
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static inline void lockdep_on(void)
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{
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}
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# define lock_acquire(l, s, t, r, c, i) do { } while (0)
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# define lock_release(l, n, i) do { } while (0)
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# define lockdep_init() do { } while (0)
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# define lockdep_info() do { } while (0)
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# define lockdep_init_map(lock, name, key, sub) do { (void)(key); } while (0)
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# define lockdep_set_class(lock, key) do { (void)(key); } while (0)
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# define lockdep_set_class_and_name(lock, key, name) \
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do { (void)(key); } while (0)
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#define lockdep_set_class_and_subclass(lock, key, sub) \
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do { (void)(key); } while (0)
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#define lockdep_set_subclass(lock, sub) do { } while (0)
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# define INIT_LOCKDEP
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# define lockdep_reset() do { debug_locks = 1; } while (0)
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# define lockdep_free_key_range(start, size) do { } while (0)
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/*
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* The class key takes no space if lockdep is disabled:
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*/
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struct lock_class_key { };
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#define lockdep_depth(tsk) (0)
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#endif /* !LOCKDEP */
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#ifdef CONFIG_LOCK_STAT
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extern void lock_contended(struct lockdep_map *lock, unsigned long ip);
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extern void lock_acquired(struct lockdep_map *lock);
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#define LOCK_CONTENDED(_lock, try, lock) \
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do { \
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if (!try(_lock)) { \
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lock_contended(&(_lock)->dep_map, _RET_IP_); \
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lock(_lock); \
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lock_acquired(&(_lock)->dep_map); \
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} \
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} while (0)
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#else /* CONFIG_LOCK_STAT */
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#define lock_contended(lockdep_map, ip) do {} while (0)
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#define lock_acquired(lockdep_map) do {} while (0)
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#define LOCK_CONTENDED(_lock, try, lock) \
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lock(_lock)
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#endif /* CONFIG_LOCK_STAT */
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#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_GENERIC_HARDIRQS)
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extern void early_init_irq_lock_class(void);
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#else
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static inline void early_init_irq_lock_class(void)
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{
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}
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#endif
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#ifdef CONFIG_TRACE_IRQFLAGS
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extern void early_boot_irqs_off(void);
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extern void early_boot_irqs_on(void);
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extern void print_irqtrace_events(struct task_struct *curr);
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#else
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static inline void early_boot_irqs_off(void)
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{
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}
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static inline void early_boot_irqs_on(void)
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{
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}
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static inline void print_irqtrace_events(struct task_struct *curr)
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{
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}
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#endif
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/*
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* For trivial one-depth nesting of a lock-class, the following
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* global define can be used. (Subsystems with multiple levels
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* of nesting should define their own lock-nesting subclasses.)
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*/
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#define SINGLE_DEPTH_NESTING 1
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/*
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* Map the dependency ops to NOP or to real lockdep ops, depending
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* on the per lock-class debug mode:
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*/
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# ifdef CONFIG_PROVE_LOCKING
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# define spin_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i)
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# else
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# define spin_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i)
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# endif
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# define spin_release(l, n, i) lock_release(l, n, i)
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#else
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# define spin_acquire(l, s, t, i) do { } while (0)
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# define spin_release(l, n, i) do { } while (0)
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# ifdef CONFIG_PROVE_LOCKING
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# define rwlock_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i)
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# define rwlock_acquire_read(l, s, t, i) lock_acquire(l, s, t, 2, 2, i)
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# else
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# define rwlock_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i)
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# define rwlock_acquire_read(l, s, t, i) lock_acquire(l, s, t, 2, 1, i)
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# endif
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# define rwlock_release(l, n, i) lock_release(l, n, i)
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#else
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# define rwlock_acquire(l, s, t, i) do { } while (0)
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# define rwlock_acquire_read(l, s, t, i) do { } while (0)
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# define rwlock_release(l, n, i) do { } while (0)
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# ifdef CONFIG_PROVE_LOCKING
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# define mutex_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i)
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# else
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# define mutex_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i)
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# endif
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# define mutex_release(l, n, i) lock_release(l, n, i)
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#else
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# define mutex_acquire(l, s, t, i) do { } while (0)
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# define mutex_release(l, n, i) do { } while (0)
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# ifdef CONFIG_PROVE_LOCKING
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# define rwsem_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i)
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# define rwsem_acquire_read(l, s, t, i) lock_acquire(l, s, t, 1, 2, i)
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# else
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# define rwsem_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i)
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# define rwsem_acquire_read(l, s, t, i) lock_acquire(l, s, t, 1, 1, i)
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# endif
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# define rwsem_release(l, n, i) lock_release(l, n, i)
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#else
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# define rwsem_acquire(l, s, t, i) do { } while (0)
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# define rwsem_acquire_read(l, s, t, i) do { } while (0)
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# define rwsem_release(l, n, i) do { } while (0)
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#endif
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#endif /* __LINUX_LOCKDEP_H */
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