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locking/lockdep: Remove the unnecessary trace saving

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In print_bad_irq_dependency(), save_trace() is called to set the ->trace
for @prev_root as the current call trace, however @prev_root corresponds
to the the held lock, which may not be acquired in current call trace,
therefore it's wrong to use save_trace() to set ->trace of @prev_root.
Moreover, with our adjustment of printing backwards dependency path, the
->trace of @prev_root is unncessary, so remove it.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210618170110.3699115-3-boqun.feng@gmail.com
This commit is contained in:
Boqun Feng 2021-06-19 01:01:08 +08:00 committed by Peter Zijlstra
parent 69c7a5fb24
commit d4c157c7b1
1 changed files with 0 additions and 3 deletions
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3
kernel/locking/lockdep.c
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@ -2550,9 +2550,6 @@ print_bad_irq_dependency(struct task_struct *curr,
lockdep_print_held_locks(curr);
pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
prev_root->trace = save_trace();
if (!prev_root->trace)
return;
print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
pr_warn("\nthe dependencies between the lock to be acquired");