Hi, On Fri, Oct 09, 2020 at 09:41:24AM -0400, Qian Cai wrote: > On Fri, 2020-10-09 at 07:58 +0000, tip-bot2 for Peter Zijlstra wrote: > > The following commit has been merged into the locking/core branch of tip: > > > > Commit-ID: 4d004099a668c41522242aa146a38cc4eb59cb1e > > Gitweb: > > https://git.kernel.org/tip/4d004099a668c41522242aa146a38cc4eb59cb1e > > Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > AuthorDate: Fri, 02 Oct 2020 11:04:21 +02:00 > > Committer: Ingo Molnar <mingo@xxxxxxxxxx> > > CommitterDate: Fri, 09 Oct 2020 08:53:30 +02:00 > > > > lockdep: Fix lockdep recursion > > > > Steve reported that lockdep_assert*irq*(), when nested inside lockdep > > itself, will trigger a false-positive. > > > > One example is the stack-trace code, as called from inside lockdep, > > triggering tracing, which in turn calls RCU, which then uses > > lockdep_assert_irqs_disabled(). > > > > Fixes: a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu > > variables") > > Reported-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > > Reverting this linux-next commit fixed booting RCU-list warnings everywhere. > I think this happened because in this commit debug_lockdep_rcu_enabled() didn't adopt to the change that made lockdep_recursion a percpu variable? Qian, mind to try the following? Although, arguably the problem still exists, i.e. we still have an RCU read-side critical section inside lock_acquire(), which may be called on a yet-to-online CPU, which RCU doesn't watch. I think this used to be OK because we don't "free" anything from lockdep, IOW, there is no synchronize_rcu() or call_rcu() that _needs_ to wait for the RCU read-side critical sections inside lockdep. But now we lock class recycling, so it might be a problem. That said, currently validate_chain() and lock class recycling are mutually excluded via graph_lock, so we are safe for this one ;-) ----------->8 diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 39334d2d2b37..35d9bab65b75 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -275,8 +275,8 @@ EXPORT_SYMBOL_GPL(rcu_callback_map); noinstr int notrace debug_lockdep_rcu_enabled(void) { - return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && - current->lockdep_recursion == 0; + return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && + __lockdep_enabled; } EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); > == x86 == > [ 8.101841][ T1] rcu: Hierarchical SRCU implementation. > [ 8.110615][ T5] NMI watchdog: Enabled. Permanently consumes one hw-PMU counter. > [ 8.153506][ T1] smp: Bringing up secondary CPUs ... > [ 8.163075][ T1] x86: Booting SMP configuration: > [ 8.167843][ T1] .... node #0, CPUs: #1 > [ 4.002695][ T0] > [ 4.002695][ T0] ============================= > [ 4.002695][ T0] WARNING: suspicious RCU usage > [ 4.002695][ T0] 5.9.0-rc8-next-20201009 #2 Not tainted > [ 4.002695][ T0] ----------------------------- > [ 4.002695][ T0] kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!! > [ 4.002695][ T0] > [ 4.002695][ T0] other info that might help us debug this: > [ 4.002695][ T0] > [ 4.002695][ T0] > [ 4.002695][ T0] RCU used illegally from offline CPU! > [ 4.002695][ T0] rcu_scheduler_active = 1, debug_locks = 1 > [ 4.002695][ T0] no locks held by swapper/1/0. > [ 4.002695][ T0] > [ 4.002695][ T0] stack backtrace: > [ 4.002695][ T0] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.9.0-rc8-next-20201009 #2 > [ 4.002695][ T0] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 > [ 4.002695][ T0] Call Trace: > [ 4.002695][ T0] dump_stack+0x99/0xcb > [ 4.002695][ T0] __lock_acquire.cold.76+0x2ad/0x3e0 > lookup_chain_cache at kernel/locking/lockdep.c:3497 > (inlined by) lookup_chain_cache_add at kernel/locking/lockdep.c:3517 > (inlined by) validate_chain at kernel/locking/lockdep.c:3572 > (inlined by) __lock_acquire at kernel/locking/lockdep.c:4837 > [ 4.002695][ T0] ? lockdep_hardirqs_on_prepare+0x3d0/0x3d0 > [ 4.002695][ T0] lock_acquire+0x1c8/0x820 > lockdep_recursion_finish at kernel/locking/lockdep.c:435 > (inlined by) lock_acquire at kernel/locking/lockdep.c:5444 > (inlined by) lock_acquire at kernel/locking/lockdep.c:5407 > [ 4.002695][ T0] ? __debug_object_init+0xb4/0xf50 > [ 4.002695][ T0] ? memset+0x1f/0x40 > [ 4.002695][ T0] ? rcu_read_unlock+0x40/0x40 > [ 4.002695][ T0] ? mce_gather_info+0x170/0x170 > [ 4.002695][ T0] ? arch_freq_get_on_cpu+0x270/0x270 > [ 4.002695][ T0] ? mce_cpu_restart+0x40/0x40 > [ 4.002695][ T0] _raw_spin_lock_irqsave+0x30/0x50 > [ 4.002695][ T0] ? __debug_object_init+0xb4/0xf50 > [ 4.002695][ T0] __debug_object_init+0xb4/0xf50 > [ 4.002695][ T0] ? mce_amd_feature_init+0x80c/0xa70 > [ 4.002695][ T0] ? debug_object_fixup+0x30/0x30 > [ 4.002695][ T0] ? machine_check_poll+0x2d0/0x2d0 > [ 4.002695][ T0] ? mce_cpu_restart+0x40/0x40 > [ 4.002695][ T0] init_timer_key+0x29/0x220 > [ 4.002695][ T0] identify_cpu+0xfcb/0x1980 > [ 4.002695][ T0] identify_secondary_cpu+0x1d/0x190 > [ 4.002695][ T0] smp_store_cpu_info+0x167/0x1f0 > [ 4.002695][ T0] start_secondary+0x5b/0x290 > [ 4.002695][ T0] secondary_startup_64_no_verify+0xb8/0xbb > [ 8.379508][ T1] #2 > [ 8.389728][ T1] #3 > [ 8.399901][ T1] > > == s390 == > 00: [ 1.539768] rcu: Hierarchical SRCU implementation. > 00: [ 1.561622] smp: Bringing up secondary CPUs ... > 00: [ 1.568677] > 00: [ 1.568681] ============================= > 00: [ 1.568682] WARNING: suspicious RCU usage > 00: [ 1.568688] 5.9.0-rc8-next-20201009 #2 Not tainted > 00: [ 1.568688] ----------------------------- > 00: [ 1.568691] kernel/locking/lockdep.c:3497 RCU-list traversed in non-reade > 00: r section!! > 00: [ 1.568692] > 00: [ 1.568692] other info that might help us debug this: > 00: [ 1.568692] > 00: [ 1.568694] > 00: [ 1.568694] RCU used illegally from offline CPU! > 00: [ 1.568694] rcu_scheduler_active = 1, debug_locks = 1 > 00: [ 1.568697] no locks held by swapper/1/0. > 00: [ 1.568697] > 00: [ 1.568697] stack backtrace: > 00: [ 1.568702] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.9.0-rc8-next-2020 > 00: 1009 #2 > 00: [ 1.568704] Hardware name: IBM 2964 N96 400 (z/VM 6.4.0) > 00: [ 1.568706] Call Trace: > 00: [ 1.568719] [<000000011fb85370>] show_stack+0x158/0x1f0 > 00: [ 1.568723] [<000000011fb90402>] dump_stack+0x1f2/0x238 > 00: [ 1.568730] [<000000011ebd89d8>] __lock_acquire+0x2640/0x4dd0 > lookup_chain_cache at kernel/locking/lockdep.c:3497 > (inlined by) lookup_chain_cache_add at kernel/locking/lockdep.c:3517 > (inlined by) validate_chain at kernel/locking/lockdep.c:3572 > (inlined by) __lock_acquire at kernel/locking/lockdep.c:4837 > 00: [ 1.568732] [<000000011ebdd230>] lock_acquire+0x3a8/0xd08 > lockdep_recursion_finish at kernel/locking/lockdep.c:435 > (inlined by) lock_acquire at kernel/locking/lockdep.c:5444 > (inlined by) lock_acquire at kernel/locking/lockdep.c:5407 > 00: [ 1.568738] [<000000011fbb5ca8>] _raw_spin_lock_irqsave+0xc0/0xf0 > __raw_spin_lock_irqsave at include/linux/spinlock_api_smp.h:117 > (inlined by) _raw_spin_lock_irqsave at kernel/locking/spinlock.c:159 > 00: [ 1.568745] [<000000011ec6e7e8>] clockevents_register_device+0xa8/0x528 > 00: > 00: [ 1.568748] [<000000011ea55246>] init_cpu_timer+0x33e/0x468 > 00: [ 1.568754] [<000000011ea7f4d2>] smp_init_secondary+0x11a/0x328 > 00: [ 1.568757] [<000000011ea7f3b2>] smp_start_secondary+0x82/0x88 > smp_start_secondary at arch/s390/kernel/smp.c:892 > 00: [ 1.568759] no locks held by swapper/1/0. > 00: [ 1.569956] smp: Brought up 1 node, 2 CPUs > > > --- > > include/linux/lockdep.h | 13 +++-- > > kernel/locking/lockdep.c | 99 ++++++++++++++++++++++---------------- > > 2 files changed, 67 insertions(+), 45 deletions(-) > > > > diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h > > index 6a584b3..b1227be 100644 > > --- a/include/linux/lockdep.h > > +++ b/include/linux/lockdep.h > > @@ -534,6 +534,7 @@ do { > > \ > > > > DECLARE_PER_CPU(int, hardirqs_enabled); > > DECLARE_PER_CPU(int, hardirq_context); > > +DECLARE_PER_CPU(unsigned int, lockdep_recursion); > > > > /* > > * The below lockdep_assert_*() macros use raw_cpu_read() to access the above > > @@ -543,25 +544,27 @@ DECLARE_PER_CPU(int, hardirq_context); > > * read the value from our previous CPU. > > */ > > > > +#define __lockdep_enabled (debug_locks && > > !raw_cpu_read(lockdep_recursion)) > > + > > #define lockdep_assert_irqs_enabled() > > \ > > do { \ > > - WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirqs_enabled)); \ > > + WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirqs_enabled)); \ > > } while (0) > > > > #define lockdep_assert_irqs_disabled() > > \ > > do { \ > > - WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled)); \ > > + WARN_ON_ONCE(__lockdep_enabled && raw_cpu_read(hardirqs_enabled)); \ > > } while (0) > > > > #define lockdep_assert_in_irq() > > \ > > do { \ > > - WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirq_context)); \ > > + WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirq_context)); \ > > } while (0) > > > > #define lockdep_assert_preemption_enabled() \ > > do { \ > > WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \ > > - debug_locks && \ > > + __lockdep_enabled && \ > > (preempt_count() != 0 || \ > > !raw_cpu_read(hardirqs_enabled))); \ > > } while (0) > > @@ -569,7 +572,7 @@ do { > > \ > > #define lockdep_assert_preemption_disabled() \ > > do { \ > > WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \ > > - debug_locks && \ > > + __lockdep_enabled && \ > > (preempt_count() == 0 && \ > > raw_cpu_read(hardirqs_enabled))); \ > > } while (0) > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > > index a430fbb..85d15f0 100644 > > --- a/kernel/locking/lockdep.c > > +++ b/kernel/locking/lockdep.c > > @@ -76,6 +76,23 @@ module_param(lock_stat, int, 0644); > > #define lock_stat 0 > > #endif > > > > +DEFINE_PER_CPU(unsigned int, lockdep_recursion); > > +EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion); > > + > > +static inline bool lockdep_enabled(void) > > +{ > > + if (!debug_locks) > > + return false; > > + > > + if (raw_cpu_read(lockdep_recursion)) > > + return false; > > + > > + if (current->lockdep_recursion) > > + return false; > > + > > + return true; > > +} > > + > > /* > > * lockdep_lock: protects the lockdep graph, the hashes and the > > * class/list/hash allocators. > > @@ -93,7 +110,7 @@ static inline void lockdep_lock(void) > > > > arch_spin_lock(&__lock); > > __owner = current; > > - current->lockdep_recursion++; > > + __this_cpu_inc(lockdep_recursion); > > } > > > > static inline void lockdep_unlock(void) > > @@ -101,7 +118,7 @@ static inline void lockdep_unlock(void) > > if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current)) > > return; > > > > - current->lockdep_recursion--; > > + __this_cpu_dec(lockdep_recursion); > > __owner = NULL; > > arch_spin_unlock(&__lock); > > } > > @@ -393,10 +410,15 @@ void lockdep_init_task(struct task_struct *task) > > task->lockdep_recursion = 0; > > } > > > > +static __always_inline void lockdep_recursion_inc(void) > > +{ > > + __this_cpu_inc(lockdep_recursion); > > +} > > + > > static __always_inline void lockdep_recursion_finish(void) > > { > > - if (WARN_ON_ONCE((--current->lockdep_recursion) & > > LOCKDEP_RECURSION_MASK)) > > - current->lockdep_recursion = 0; > > + if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion))) > > + __this_cpu_write(lockdep_recursion, 0); > > } > > > > void lockdep_set_selftest_task(struct task_struct *task) > > @@ -3659,7 +3681,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip) > > if (unlikely(in_nmi())) > > return; > > > > - if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) > > + if (unlikely(__this_cpu_read(lockdep_recursion))) > > return; > > > > if (unlikely(lockdep_hardirqs_enabled())) { > > @@ -3695,7 +3717,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip) > > > > current->hardirq_chain_key = current->curr_chain_key; > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > __trace_hardirqs_on_caller(); > > lockdep_recursion_finish(); > > } > > @@ -3728,7 +3750,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip) > > goto skip_checks; > > } > > > > - if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) > > + if (unlikely(__this_cpu_read(lockdep_recursion))) > > return; > > > > if (lockdep_hardirqs_enabled()) { > > @@ -3781,7 +3803,7 @@ void noinstr lockdep_hardirqs_off(unsigned long ip) > > if (in_nmi()) { > > if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) > > return; > > - } else if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK) > > + } else if (__this_cpu_read(lockdep_recursion)) > > return; > > > > /* > > @@ -3814,7 +3836,7 @@ void lockdep_softirqs_on(unsigned long ip) > > { > > struct irqtrace_events *trace = ¤t->irqtrace; > > > > - if (unlikely(!debug_locks || current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return; > > > > /* > > @@ -3829,7 +3851,7 @@ void lockdep_softirqs_on(unsigned long ip) > > return; > > } > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > /* > > * We'll do an OFF -> ON transition: > > */ > > @@ -3852,7 +3874,7 @@ void lockdep_softirqs_on(unsigned long ip) > > */ > > void lockdep_softirqs_off(unsigned long ip) > > { > > - if (unlikely(!debug_locks || current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return; > > > > /* > > @@ -4233,11 +4255,11 @@ void lockdep_init_map_waits(struct lockdep_map *lock, > > const char *name, > > if (subclass) { > > unsigned long flags; > > > > - if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion)) > > + if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > register_lock_class(lock, subclass, 1); > > lockdep_recursion_finish(); > > raw_local_irq_restore(flags); > > @@ -4920,11 +4942,11 @@ void lock_set_class(struct lockdep_map *lock, const > > char *name, > > { > > unsigned long flags; > > > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > check_flags(flags); > > if (__lock_set_class(lock, name, key, subclass, ip)) > > check_chain_key(current); > > @@ -4937,11 +4959,11 @@ void lock_downgrade(struct lockdep_map *lock, unsigned > > long ip) > > { > > unsigned long flags; > > > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > check_flags(flags); > > if (__lock_downgrade(lock, ip)) > > check_chain_key(current); > > @@ -4979,7 +5001,7 @@ static void verify_lock_unused(struct lockdep_map *lock, > > struct held_lock *hlock > > > > static bool lockdep_nmi(void) > > { > > - if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK) > > + if (raw_cpu_read(lockdep_recursion)) > > return false; > > > > if (!in_nmi()) > > @@ -5000,7 +5022,10 @@ void lock_acquire(struct lockdep_map *lock, unsigned > > int subclass, > > > > trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip); > > > > - if (unlikely(current->lockdep_recursion)) { > > + if (!debug_locks) > > + return; > > + > > + if (unlikely(!lockdep_enabled())) { > > /* XXX allow trylock from NMI ?!? */ > > if (lockdep_nmi() && !trylock) { > > struct held_lock hlock; > > @@ -5023,7 +5048,7 @@ void lock_acquire(struct lockdep_map *lock, unsigned int > > subclass, > > raw_local_irq_save(flags); > > check_flags(flags); > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > __lock_acquire(lock, subclass, trylock, read, check, > > irqs_disabled_flags(flags), nest_lock, ip, 0, 0); > > lockdep_recursion_finish(); > > @@ -5037,13 +5062,13 @@ void lock_release(struct lockdep_map *lock, unsigned > > long ip) > > > > trace_lock_release(lock, ip); > > > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > check_flags(flags); > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > if (__lock_release(lock, ip)) > > check_chain_key(current); > > lockdep_recursion_finish(); > > @@ -5056,13 +5081,13 @@ noinstr int lock_is_held_type(const struct lockdep_map > > *lock, int read) > > unsigned long flags; > > int ret = 0; > > > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return 1; /* avoid false negative lockdep_assert_held() */ > > > > raw_local_irq_save(flags); > > check_flags(flags); > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > ret = __lock_is_held(lock, read); > > lockdep_recursion_finish(); > > raw_local_irq_restore(flags); > > @@ -5077,13 +5102,13 @@ struct pin_cookie lock_pin_lock(struct lockdep_map > > *lock) > > struct pin_cookie cookie = NIL_COOKIE; > > unsigned long flags; > > > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return cookie; > > > > raw_local_irq_save(flags); > > check_flags(flags); > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > cookie = __lock_pin_lock(lock); > > lockdep_recursion_finish(); > > raw_local_irq_restore(flags); > > @@ -5096,13 +5121,13 @@ void lock_repin_lock(struct lockdep_map *lock, struct > > pin_cookie cookie) > > { > > unsigned long flags; > > > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > check_flags(flags); > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > __lock_repin_lock(lock, cookie); > > lockdep_recursion_finish(); > > raw_local_irq_restore(flags); > > @@ -5113,13 +5138,13 @@ void lock_unpin_lock(struct lockdep_map *lock, struct > > pin_cookie cookie) > > { > > unsigned long flags; > > > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > check_flags(flags); > > > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > __lock_unpin_lock(lock, cookie); > > lockdep_recursion_finish(); > > raw_local_irq_restore(flags); > > @@ -5249,15 +5274,12 @@ void lock_contended(struct lockdep_map *lock, unsigned > > long ip) > > > > trace_lock_acquired(lock, ip); > > > > - if (unlikely(!lock_stat || !debug_locks)) > > - return; > > - > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lock_stat || !lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > check_flags(flags); > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > __lock_contended(lock, ip); > > lockdep_recursion_finish(); > > raw_local_irq_restore(flags); > > @@ -5270,15 +5292,12 @@ void lock_acquired(struct lockdep_map *lock, unsigned > > long ip) > > > > trace_lock_contended(lock, ip); > > > > - if (unlikely(!lock_stat || !debug_locks)) > > - return; > > - > > - if (unlikely(current->lockdep_recursion)) > > + if (unlikely(!lock_stat || !lockdep_enabled())) > > return; > > > > raw_local_irq_save(flags); > > check_flags(flags); > > - current->lockdep_recursion++; > > + lockdep_recursion_inc(); > > __lock_acquired(lock, ip); > > lockdep_recursion_finish(); > > raw_local_irq_restore(flags); >
