6.6-stable review patch. If anyone has any objections, please let me know.
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From: Ryo Takakura ryotkkr98@gmail.com
[ Upstream commit 61c39d8c83e2077f33e0a2c8980a76a7f323f0ce ]
Since:
0c1d7a2c2d32 ("lockdep: Remove softirq accounting on PREEMPT_RT.")
the wait context test for mutex usage within "in softirq context" fails as it references @softirq_context:
| wait context tests | -------------------------------------------------------------------------- | rcu | raw | spin |mutex | -------------------------------------------------------------------------- in hardirq context: ok | ok | ok | ok | in hardirq context (not threaded): ok | ok | ok | ok | in softirq context: ok | ok | ok |FAILED|
As a fix, add lockdep map for BH disabled section. This fixes the issue by letting us catch cases when local_bh_disable() gets called with preemption disabled where local_lock doesn't get acquired. In the case of "in softirq context" selftest, local_bh_disable() was being called with preemption disable as it's early in the boot.
[ boqun: Move the lockdep annotations into __local_bh_*() to avoid false positives because of unpaired local_bh_disable() reported by Borislav Petkov and Peter Zijlstra, and make bh_lock_map only exist for PREEMPT_RT. ]
[ mingo: Restored authorship and improved the bh_lock_map definition. ]
Signed-off-by: Ryo Takakura ryotkkr98@gmail.com Signed-off-by: Boqun Feng boqun.feng@gmail.com Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lore.kernel.org/r/20250321143322.79651-1-boqun.feng@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/softirq.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/kernel/softirq.c b/kernel/softirq.c index f24d80cf20bd3..d9e37f3fa1303 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -125,6 +125,18 @@ static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = { .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock), };
+#ifdef CONFIG_DEBUG_LOCK_ALLOC +static struct lock_class_key bh_lock_key; +struct lockdep_map bh_lock_map = { + .name = "local_bh", + .key = &bh_lock_key, + .wait_type_outer = LD_WAIT_FREE, + .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */ + .lock_type = LD_LOCK_PERCPU, +}; +EXPORT_SYMBOL_GPL(bh_lock_map); +#endif + /** * local_bh_blocked() - Check for idle whether BH processing is blocked * @@ -147,6 +159,8 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
WARN_ON_ONCE(in_hardirq());
+ lock_map_acquire_read(&bh_lock_map); + /* First entry of a task into a BH disabled section? */ if (!current->softirq_disable_cnt) { if (preemptible()) { @@ -210,6 +224,8 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) WARN_ON_ONCE(in_hardirq()); lockdep_assert_irqs_enabled();
+ lock_map_release(&bh_lock_map); + local_irq_save(flags); curcnt = __this_cpu_read(softirq_ctrl.cnt);
@@ -260,6 +276,8 @@ static inline void ksoftirqd_run_begin(void) /* Counterpart to ksoftirqd_run_begin() */ static inline void ksoftirqd_run_end(void) { + /* pairs with the lock_map_acquire_read() in ksoftirqd_run_begin() */ + lock_map_release(&bh_lock_map); __local_bh_enable(SOFTIRQ_OFFSET, true); WARN_ON_ONCE(in_interrupt()); local_irq_enable();