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authorLinus Torvalds <torvalds@linux-foundation.org>2020-04-12 09:47:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-12 09:47:10 -0700
commit652fa53caa01dbfdef1b8c5997767e284ac21a5c (patch)
treed4a0998c9501a6f525ac269169865613a123be16 /kernel
parent4119bf9f1d093b495f5fe3fcb32bde3156d2ba6e (diff)
parent9a019db0b6bebc84d6b64636faf73ed6d64cd4bb (diff)
downloadlinux-652fa53caa01dbfdef1b8c5997767e284ac21a5c.tar.bz2
Merge tag 'locking-urgent-2020-04-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner: "Three small fixes/updates for the locking core code: - Plug a task struct reference leak in the percpu rswem implementation. - Document the refcount interaction with PID_MAX_LIMIT - Improve the 'invalid wait context' data dump in lockdep so it contains all information which is required to decode the problem" * tag 'locking-urgent-2020-04-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking/lockdep: Improve 'invalid wait context' splat locking/refcount: Document interaction with PID_MAX_LIMIT locking/percpu-rwsem: Fix a task_struct refcount
Diffstat (limited to 'kernel')
-rw-r--r--kernel/locking/lockdep.c51
-rw-r--r--kernel/locking/percpu-rwsem.c3
2 files changed, 33 insertions, 21 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1511690e4de7..ac10db66cc63 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3952,10 +3952,36 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
return ret;
}
+static inline short task_wait_context(struct task_struct *curr)
+{
+ /*
+ * Set appropriate wait type for the context; for IRQs we have to take
+ * into account force_irqthread as that is implied by PREEMPT_RT.
+ */
+ if (curr->hardirq_context) {
+ /*
+ * Check if force_irqthreads will run us threaded.
+ */
+ if (curr->hardirq_threaded || curr->irq_config)
+ return LD_WAIT_CONFIG;
+
+ return LD_WAIT_SPIN;
+ } else if (curr->softirq_context) {
+ /*
+ * Softirqs are always threaded.
+ */
+ return LD_WAIT_CONFIG;
+ }
+
+ return LD_WAIT_MAX;
+}
+
static int
print_lock_invalid_wait_context(struct task_struct *curr,
struct held_lock *hlock)
{
+ short curr_inner;
+
if (!debug_locks_off())
return 0;
if (debug_locks_silent)
@@ -3971,6 +3997,10 @@ print_lock_invalid_wait_context(struct task_struct *curr,
print_lock(hlock);
pr_warn("other info that might help us debug this:\n");
+
+ curr_inner = task_wait_context(curr);
+ pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
+
lockdep_print_held_locks(curr);
pr_warn("stack backtrace:\n");
@@ -4017,26 +4047,7 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
}
depth++;
- /*
- * Set appropriate wait type for the context; for IRQs we have to take
- * into account force_irqthread as that is implied by PREEMPT_RT.
- */
- if (curr->hardirq_context) {
- /*
- * Check if force_irqthreads will run us threaded.
- */
- if (curr->hardirq_threaded || curr->irq_config)
- curr_inner = LD_WAIT_CONFIG;
- else
- curr_inner = LD_WAIT_SPIN;
- } else if (curr->softirq_context) {
- /*
- * Softirqs are always threaded.
- */
- curr_inner = LD_WAIT_CONFIG;
- } else {
- curr_inner = LD_WAIT_MAX;
- }
+ curr_inner = task_wait_context(curr);
for (; depth < curr->lockdep_depth; depth++) {
struct held_lock *prev = curr->held_locks + depth;
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index a008a1ba21a7..8bbafe3e5203 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -118,14 +118,15 @@ static int percpu_rwsem_wake_function(struct wait_queue_entry *wq_entry,
unsigned int mode, int wake_flags,
void *key)
{
- struct task_struct *p = get_task_struct(wq_entry->private);
bool reader = wq_entry->flags & WQ_FLAG_CUSTOM;
struct percpu_rw_semaphore *sem = key;
+ struct task_struct *p;
/* concurrent against percpu_down_write(), can get stolen */
if (!__percpu_rwsem_trylock(sem, reader))
return 1;
+ p = get_task_struct(wq_entry->private);
list_del_init(&wq_entry->entry);
smp_store_release(&wq_entry->private, NULL);