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locking/lockdep: Untangle xhlock history save/restore from task independence

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Where XHLOCK_{SOFT,HARD} are save/restore points in the xhlocks[] to
ensure the temporal IRQ events don't interact with task state, the
XHLOCK_PROC is a fundament different beast that just happens to share
the interface.

The purpose of XHLOCK_PROC is to annotate independent execution inside
one task. For example workqueues, each work should appear to run in its
own 'pristine' 'task'.

Remove XHLOCK_PROC in favour of its own interface to avoid confusion.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: david@fromorbit.com
Cc: johannes@sipsolutions.net
Cc: kernel-team@lge.com
Cc: oleg@redhat.com
Cc: tj@kernel.org
Link: http://lkml.kernel.org/r/20170829085939.ggmb6xiohw67micb@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-08-29 10:59:39 +02:00 committed by Ingo Molnar
parent 7b3d61cc73
commit f52be57080
4 changed files with 48 additions and 51 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
include/linux/irqflags.h
View file

@ -26,7 +26,7 @@
# define trace_hardirq_enter() \
do { \
current->hardirq_context++; \
crossrelease_hist_start(XHLOCK_HARD, 0);\
crossrelease_hist_start(XHLOCK_HARD); \
} while (0)
# define trace_hardirq_exit() \
do { \
@ -36,7 +36,7 @@ do { \
# define lockdep_softirq_enter() \
do { \
current->softirq_context++; \
crossrelease_hist_start(XHLOCK_SOFT, 0);\
crossrelease_hist_start(XHLOCK_SOFT); \
} while (0)
# define lockdep_softirq_exit() \
do { \

7
include/linux/lockdep.h
View file

@ -551,7 +551,6 @@ struct pin_cookie { };
enum xhlock_context_t {
XHLOCK_HARD,
XHLOCK_SOFT,
XHLOCK_PROC,
XHLOCK_CTX_NR,
};
@ -580,8 +579,9 @@ extern void lock_commit_crosslock(struct lockdep_map *lock);
#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
{ .name = (_name), .key = (void *)(_key), .cross = 0, }
extern void crossrelease_hist_start(enum xhlock_context_t c, bool force);
extern void crossrelease_hist_start(enum xhlock_context_t c);
extern void crossrelease_hist_end(enum xhlock_context_t c);
extern void lockdep_invariant_state(bool force);
extern void lockdep_init_task(struct task_struct *task);
extern void lockdep_free_task(struct task_struct *task);
#else /* !CROSSRELEASE */
@ -593,8 +593,9 @@ extern void lockdep_free_task(struct task_struct *task);
#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
{ .name = (_name), .key = (void *)(_key), }
static inline void crossrelease_hist_start(enum xhlock_context_t c, bool force) {}
static inline void crossrelease_hist_start(enum xhlock_context_t c) {}
static inline void crossrelease_hist_end(enum xhlock_context_t c) {}
static inline void lockdep_invariant_state(bool force) {}
static inline void lockdep_init_task(struct task_struct *task) {}
static inline void lockdep_free_task(struct task_struct *task) {}
#endif /* CROSSRELEASE */

79
kernel/locking/lockdep.c
View file

@ -4623,13 +4623,8 @@ asmlinkage __visible void lockdep_sys_exit(void)
/*
* The lock history for each syscall should be independent. So wipe the
* slate clean on return to userspace.
*
* crossrelease_hist_end() works well here even when getting here
* without starting (i.e. just after forking), because it rolls back
* the index to point to the last entry, which is already invalid.
*/
crossrelease_hist_end(XHLOCK_PROC);
crossrelease_hist_start(XHLOCK_PROC, false);
lockdep_invariant_state(false);
}
void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
@ -4723,19 +4718,47 @@ static inline void invalidate_xhlock(struct hist_lock *xhlock)
}
/*
* Lock history stacks; we have 3 nested lock history stacks:
* Lock history stacks; we have 2 nested lock history stacks:
*
* HARD(IRQ)
* SOFT(IRQ)
* PROC(ess)
*
* The thing is that once we complete a HARD/SOFT IRQ the future task locks
* should not depend on any of the locks observed while running the IRQ. So
* what we do is rewind the history buffer and erase all our knowledge of that
* temporal event.
*
* The PROCess one is special though; it is used to annotate independence
* inside a task.
*/
void crossrelease_hist_start(enum xhlock_context_t c)
{
struct task_struct *cur = current;
if (!cur->xhlocks)
return;
cur->xhlock_idx_hist[c] = cur->xhlock_idx;
cur->hist_id_save[c] = cur->hist_id;
}
void crossrelease_hist_end(enum xhlock_context_t c)
{
struct task_struct *cur = current;
if (cur->xhlocks) {
unsigned int idx = cur->xhlock_idx_hist[c];
struct hist_lock *h = &xhlock(idx);
cur->xhlock_idx = idx;
/* Check if the ring was overwritten. */
if (h->hist_id != cur->hist_id_save[c])
invalidate_xhlock(h);
}
}
/*
* lockdep_invariant_state() is used to annotate independence inside a task, to
* make one task look like multiple independent 'tasks'.
*
* Take for instance workqueues; each work is independent of the last. The
* completion of a future work does not depend on the completion of a past work
@ -4758,40 +4781,14 @@ static inline void invalidate_xhlock(struct hist_lock *xhlock)
* entry. Similarly, independence per-definition means it does not depend on
* prior state.
*/
void crossrelease_hist_start(enum xhlock_context_t c, bool force)
void lockdep_invariant_state(bool force)
{
struct task_struct *cur = current;
if (!cur->xhlocks)
return;
/*
* We call this at an invariant point, no current state, no history.
* Verify the former, enforce the latter.
*/
if (c == XHLOCK_PROC) {
/* verified the former, ensure the latter */
WARN_ON_ONCE(!force && cur->lockdep_depth);
invalidate_xhlock(&xhlock(cur->xhlock_idx));
}
cur->xhlock_idx_hist[c] = cur->xhlock_idx;
cur->hist_id_save[c] = cur->hist_id;
}
void crossrelease_hist_end(enum xhlock_context_t c)
{
struct task_struct *cur = current;
if (cur->xhlocks) {
unsigned int idx = cur->xhlock_idx_hist[c];
struct hist_lock *h = &xhlock(idx);
cur->xhlock_idx = idx;
/* Check if the ring was overwritten. */
if (h->hist_id != cur->hist_id_save[c])
invalidate_xhlock(h);
}
WARN_ON_ONCE(!force && current->lockdep_depth);
invalidate_xhlock(&xhlock(current->xhlock_idx));
}
static int cross_lock(struct lockdep_map *lock)

9
kernel/workqueue.c
View file

@ -2094,8 +2094,8 @@ __acquires(&pool->lock)
lock_map_acquire(&pwq->wq->lockdep_map);
lock_map_acquire(&lockdep_map);
/*
* Strictly speaking we should do start(PROC) without holding any
* locks, that is, before these two lock_map_acquire()'s.
* Strictly speaking we should mark the invariant state without holding
* any locks, that is, before these two lock_map_acquire()'s.
*
* However, that would result in:
*
@ -2107,14 +2107,14 @@ __acquires(&pool->lock)
* Which would create W1->C->W1 dependencies, even though there is no
* actual deadlock possible. There are two solutions, using a
* read-recursive acquire on the work(queue) 'locks', but this will then
* hit the lockdep limitation on recursive locks, or simly discard
* hit the lockdep limitation on recursive locks, or simply discard
* these locks.
*
* AFAICT there is no possible deadlock scenario between the
* flush_work() and complete() primitives (except for single-threaded
* workqueues), so hiding them isn't a problem.
*/
crossrelease_hist_start(XHLOCK_PROC, true);
lockdep_invariant_state(true);
trace_workqueue_execute_start(work);
worker->current_func(work);
/*
@ -2122,7 +2122,6 @@ __acquires(&pool->lock)
* point will only record its address.
*/
trace_workqueue_execute_end(work);
crossrelease_hist_end(XHLOCK_PROC);
lock_map_release(&lockdep_map);
lock_map_release(&pwq->wq->lockdep_map);