Messages in this thread | | | Date | Thu, 13 Apr 2023 00:44:42 +0800 | Subject | Re: [PATCH] mm: slub: annotate kmem_cache_node->list_lock as raw_spinlock | From | Qi Zheng <> |
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On 2023/4/12 20:47, Peter Zijlstra wrote: > On Wed, Apr 12, 2023 at 08:50:29AM +0200, Vlastimil Babka wrote: > >>> --- a/lib/debugobjects.c >>> +++ b/lib/debugobjects.c >>> @@ -562,10 +562,10 @@ __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack >>> unsigned long flags; >>> >>> /* >>> - * On RT enabled kernels the pool refill must happen in preemptible >>> + * The pool refill must happen in preemptible >>> * context: >>> */ >>> - if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) >>> + if (preemptible()) >>> fill_pool(); >> >> +CC Peterz >> >> Aha so this is in fact another case where the code is written with >> actual differences between PREEMPT_RT and !PREEMPT_RT in mind, but >> CONFIG_PROVE_RAW_LOCK_NESTING always assumes PREEMPT_RT? > > Ooh, tricky, yes. PROVE_RAW_LOCK_NESTING always follows the PREEMP_RT > rules and does not expect trickery like the above. > > Something like the completely untested below might be of help.. > > --- > diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h > index d22430840b53..f3120d6a7d9e 100644 > --- a/include/linux/lockdep_types.h > +++ b/include/linux/lockdep_types.h > @@ -33,6 +33,7 @@ enum lockdep_wait_type { > enum lockdep_lock_type { > LD_LOCK_NORMAL = 0, /* normal, catch all */ > LD_LOCK_PERCPU, /* percpu */ > + LD_LOCK_WAIT, /* annotation */ > LD_LOCK_MAX, > }; > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 50d4863974e7..a4077f5bb75b 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -2279,8 +2279,9 @@ static inline bool usage_skip(struct lock_list *entry, void *mask) > * As a result, we will skip local_lock(), when we search for irq > * inversion bugs. > */ > - if (entry->class->lock_type == LD_LOCK_PERCPU) { > - if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG)) > + if (entry->class->lock_type != LD_LOCK_NORMAL) { > + if (entry->class->lock_type == LD_LOCK_PERCPU && > + DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG)) > return false; > > return true; > @@ -4752,7 +4753,8 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next) > > for (; depth < curr->lockdep_depth; depth++) { > struct held_lock *prev = curr->held_locks + depth; > - u8 prev_inner = hlock_class(prev)->wait_type_inner; > + struct lock_class *class = hlock_class(prev); > + u8 prev_inner = class->wait_type_inner; > > if (prev_inner) { > /* > @@ -4762,6 +4764,12 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next) > * Also due to trylocks. > */ > curr_inner = min(curr_inner, prev_inner); > + > + /* > + * Allow override for annotations. > + */ > + if (unlikely(class->lock_type == LD_LOCK_WAIT)) > + curr_inner = prev_inner; > } > } > > diff --git a/lib/debugobjects.c b/lib/debugobjects.c > index df86e649d8be..fae71ef72a16 100644 > --- a/lib/debugobjects.c > +++ b/lib/debugobjects.c > @@ -565,8 +565,16 @@ __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack > * On RT enabled kernels the pool refill must happen in preemptible > * context: > */ > - if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) > + if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) { > + static lockdep_map dep_map = {
static struct lockdep_map dep_map = {
> + .name = "wait-type-override", > + .wait_type_inner = LD_WAIT_SLEEP, > + .lock_type = LD_LOCK_WAIT, > + }; > + lock_map_acquire(&dep_map); > fill_pool(); > + lock_map_release(&dep_map); > + } > > db = get_bucket((unsigned long) addr); >
I just tested the above code, and then got the following warning:
[ 0.001000][ T0] ============================= [ 0.001000][ T0] [ BUG: Invalid wait context ] [ 0.001000][ T0] 6.3.0-rc6-next-20230412+ #21 Not tainted [ 0.001000][ T0] ----------------------------- [ 0.001000][ T0] swapper/0/0 is trying to lock: [ 0.001000][ T0] ffffffff825bcb80 (wait-type-override){....}-{4:4}, at: __debug_object_init+0x0/0x590 [ 0.001000][ T0] other info that might help us debug this: [ 0.001000][ T0] context-{5:5} [ 0.001000][ T0] 2 locks held by swapper/0/0: [ 0.001000][ T0] #0: ffffffff824f5178 (timekeeper_lock){....}-{2:2}, at: timekeeping_init+0xf1/0x270 [ 0.001000][ T0] #1: ffffffff824f5008 (tk_core.seq.seqcount){....}-{0:0}, at: start_kernel+0x31a/0x800 [ 0.001000][ T0] stack backtrace: [ 0.001000][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.3.0-rc6-next-20230412+ #21 [ 0.001000][ T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 0.001000][ T0] Call Trace: [ 0.001000][ T0] <TASK> [ 0.001000][ T0] dump_stack_lvl+0x77/0xc0 [ 0.001000][ T0] __lock_acquire+0xa74/0x2960 [ 0.001000][ T0] ? save_trace+0x3f/0x320 [ 0.001000][ T0] ? add_lock_to_list+0x97/0x130 [ 0.001000][ T0] lock_acquire+0xe0/0x300 [ 0.001000][ T0] ? debug_object_active_state+0x180/0x180 [ 0.001000][ T0] __debug_object_init+0x47/0x590 [ 0.001000][ T0] ? debug_object_active_state+0x180/0x180 [ 0.001000][ T0] ? lock_acquire+0x100/0x300 [ 0.001000][ T0] hrtimer_init+0x23/0xc0 [ 0.001000][ T0] ntp_init+0x70/0x80 [ 0.001000][ T0] timekeeping_init+0x12c/0x270 [ 0.001000][ T0] ? start_kernel+0x31a/0x800 [ 0.001000][ T0] ? _printk+0x5c/0x80 [ 0.001000][ T0] start_kernel+0x31a/0x800 [ 0.001000][ T0] secondary_startup_64_no_verify+0xf4/0xfb [ 0.001000][ T0] </TASK>
It seems that the LD_WAIT_SLEEP we set is already greater than the LD_WAIT_SPIN of the current context.
-- Thanks, Qi
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