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lockdep: Fix wait context check on softirq for PREEMPT_RT

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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
This commit is contained in:
Ryo Takakura 2025-03-21 07:33:22 -07:00 committed by Ingo Molnar
parent 0e1ff67d16
commit 61c39d8c83
1 changed files with 18 additions and 0 deletions
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18
kernel/softirq.c
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@ -126,6 +126,18 @@ 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
*
@ -148,6 +160,8 @@ 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()) {
@ -211,6 +225,8 @@ 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);
@ -261,6 +277,8 @@ 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();