From 63886bad904b73f7470fd582fbc41c5ae04d6785 Mon Sep 17 00:00:00 2001 From: Qian Cai Date: Sat, 21 Mar 2020 18:22:34 -0700 Subject: mm/mmu_notifier: silence PROVE_RCU_LIST warnings It is safe to traverse mm->notifier_subscriptions->list either under SRCU read lock or mm->notifier_subscriptions->lock using hlist_for_each_entry_rcu(). Silence the PROVE_RCU_LIST false positives, for example, WARNING: suspicious RCU usage ----------------------------- mm/mmu_notifier.c:484 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by libvirtd/802: #0: ffff9321e3f58148 (&mm->mmap_sem#2){++++}, at: do_mprotect_pkey+0xe1/0x3e0 #1: ffffffff91ae6160 (mmu_notifier_invalidate_range_start){+.+.}, at: change_p4d_range+0x5fa/0x800 #2: ffffffff91ae6e08 (srcu){....}, at: __mmu_notifier_invalidate_range_start+0x178/0x460 stack backtrace: CPU: 7 PID: 802 Comm: libvirtd Tainted: G I 5.6.0-rc6-next-20200317+ #2 Hardware name: HP ProLiant BL460c Gen8, BIOS I31 11/02/2014 Call Trace: dump_stack+0xa4/0xfe lockdep_rcu_suspicious+0xeb/0xf5 __mmu_notifier_invalidate_range_start+0x3ff/0x460 change_p4d_range+0x746/0x800 change_protection+0x1df/0x300 mprotect_fixup+0x245/0x3e0 do_mprotect_pkey+0x23b/0x3e0 __x64_sys_mprotect+0x51/0x70 do_syscall_64+0x91/0xae8 entry_SYSCALL_64_after_hwframe+0x49/0xb3 Signed-off-by: Qian Cai Signed-off-by: Andrew Morton Reviewed-by: Paul E. McKenney Reviewed-by: Jason Gunthorpe Link: http://lkml.kernel.org/r/20200317175640.2047-1-cai@lca.pw Signed-off-by: Linus Torvalds --- mm/mmu_notifier.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index ef3973a5d34a..06852b896fa6 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -307,7 +307,8 @@ static void mn_hlist_release(struct mmu_notifier_subscriptions *subscriptions, * ->release returns. */ id = srcu_read_lock(&srcu); - hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist) + hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) /* * If ->release runs before mmu_notifier_unregister it must be * handled, as it's the only way for the driver to flush all @@ -370,7 +371,8 @@ int __mmu_notifier_clear_flush_young(struct mm_struct *mm, id = srcu_read_lock(&srcu); hlist_for_each_entry_rcu(subscription, - &mm->notifier_subscriptions->list, hlist) { + &mm->notifier_subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { if (subscription->ops->clear_flush_young) young |= subscription->ops->clear_flush_young( subscription, mm, start, end); @@ -389,7 +391,8 @@ int __mmu_notifier_clear_young(struct mm_struct *mm, id = srcu_read_lock(&srcu); hlist_for_each_entry_rcu(subscription, - &mm->notifier_subscriptions->list, hlist) { + &mm->notifier_subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { if (subscription->ops->clear_young) young |= subscription->ops->clear_young(subscription, mm, start, end); @@ -407,7 +410,8 @@ int __mmu_notifier_test_young(struct mm_struct *mm, id = srcu_read_lock(&srcu); hlist_for_each_entry_rcu(subscription, - &mm->notifier_subscriptions->list, hlist) { + &mm->notifier_subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { if (subscription->ops->test_young) { young = subscription->ops->test_young(subscription, mm, address); @@ -428,7 +432,8 @@ void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, id = srcu_read_lock(&srcu); hlist_for_each_entry_rcu(subscription, - &mm->notifier_subscriptions->list, hlist) { + &mm->notifier_subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { if (subscription->ops->change_pte) subscription->ops->change_pte(subscription, mm, address, pte); @@ -476,7 +481,8 @@ static int mn_hlist_invalidate_range_start( int id; id = srcu_read_lock(&srcu); - hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist) { + hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { const struct mmu_notifier_ops *ops = subscription->ops; if (ops->invalidate_range_start) { @@ -528,7 +534,8 @@ mn_hlist_invalidate_end(struct mmu_notifier_subscriptions *subscriptions, int id; id = srcu_read_lock(&srcu); - hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist) { + hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { /* * Call invalidate_range here too to avoid the need for the * subsystem of having to register an invalidate_range_end @@ -582,7 +589,8 @@ void __mmu_notifier_invalidate_range(struct mm_struct *mm, id = srcu_read_lock(&srcu); hlist_for_each_entry_rcu(subscription, - &mm->notifier_subscriptions->list, hlist) { + &mm->notifier_subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { if (subscription->ops->invalidate_range) subscription->ops->invalidate_range(subscription, mm, start, end); @@ -714,7 +722,8 @@ find_get_mmu_notifier(struct mm_struct *mm, const struct mmu_notifier_ops *ops) spin_lock(&mm->notifier_subscriptions->lock); hlist_for_each_entry_rcu(subscription, - &mm->notifier_subscriptions->list, hlist) { + &mm->notifier_subscriptions->list, hlist, + lockdep_is_held(&mm->notifier_subscriptions->lock)) { if (subscription->ops != ops) continue; -- cgit