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Commit43be438

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fbqPeter Zijlstra
authored and
Peter Zijlstra
committed
lockdep: Put graph lock/unlock under lock_recursion protection
A warning was hit when running xfstests/generic/068 in a Hyper-V guest:[...] ------------[ cut here ]------------[...] DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())[...] WARNING: CPU: 2 PID: 1350 at kernel/locking/lockdep.c:5280 check_flags.part.0+0x165/0x170[...] ...[...] Workqueue: events pwq_unbound_release_workfn[...] RIP: 0010:check_flags.part.0+0x165/0x170[...] ...[...] Call Trace:[...] lock_is_held_type+0x72/0x150[...] ? lock_acquire+0x16e/0x4a0[...] rcu_read_lock_sched_held+0x3f/0x80[...] __send_ipi_one+0x14d/0x1b0[...] hv_send_ipi+0x12/0x30[...] __pv_queued_spin_unlock_slowpath+0xd1/0x110[...] __raw_callee_save___pv_queued_spin_unlock_slowpath+0x11/0x20[...] .slowpath+0x9/0xe[...] lockdep_unregister_key+0x128/0x180[...] pwq_unbound_release_workfn+0xbb/0xf0[...] process_one_work+0x227/0x5c0[...] worker_thread+0x55/0x3c0[...] ? process_one_work+0x5c0/0x5c0[...] kthread+0x153/0x170[...] ? __kthread_bind_mask+0x60/0x60[...] ret_from_fork+0x1f/0x30The cause of the problem is we have call chain lockdep_unregister_key()-> <irq disabled by raw_local_irq_save()> lockdep_unlock() ->arch_spin_unlock() -> __pv_queued_spin_unlock_slowpath() -> pv_kick() ->__send_ipi_one() -> trace_hyperv_send_ipi_one().Although this particular warning is triggered because Hyper-V has atrace point in ipi sending, but in general arch_spin_unlock() may callanother function having a trace point in it, so put the arch_spin_lock()and arch_spin_unlock() after lock_recursion protection to fix thisproblem and avoid similiar problems.Signed-off-by: Boqun Feng <boqun.feng@gmail.com>Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>Link:https://lkml.kernel.org/r/20201113110512.1056501-1-boqun.feng@gmail.com
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‎kernel/locking/lockdep.c‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -108,19 +108,21 @@ static inline void lockdep_lock(void)
108108
{
109109
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
110110

111+
__this_cpu_inc(lockdep_recursion);
111112
arch_spin_lock(&__lock);
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__owner=current;
113-
__this_cpu_inc(lockdep_recursion);
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}
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116116
staticinlinevoidlockdep_unlock(void)
117117
{
118+
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
119+
118120
if (debug_locks&&DEBUG_LOCKS_WARN_ON(__owner!=current))
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return;
120122

121-
__this_cpu_dec(lockdep_recursion);
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__owner=NULL;
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arch_spin_unlock(&__lock);
125+
__this_cpu_dec(lockdep_recursion);
124126
}
125127

126128
staticinlineboollockdep_assert_locked(void)

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