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Subject[tip: locking/urgent] locking/lockdep: Improve 'invalid wait context' splat
The following commit has been merged into the locking/urgent branch of tip:

Commit-ID: 9a019db0b6bebc84d6b64636faf73ed6d64cd4bb
Gitweb: https://git.kernel.org/tip/9a019db0b6bebc84d6b64636faf73ed6d64cd4bb
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 31 Mar 2020 20:38:12 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 08 Apr 2020 12:05:07 +02:00

locking/lockdep: Improve 'invalid wait context' splat

The 'invalid wait context' splat doesn't print all the information
required to reconstruct / validate the error, specifically the
irq-context state is missing.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/lockdep.c | 51 +++++++++++++++++++++++----------------
1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1511690..ac10db6 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;
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