From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B48E2C433F5 for ; Wed, 2 Feb 2022 15:58:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345606AbiBBP6a (ORCPT ); Wed, 2 Feb 2022 10:58:30 -0500 Received: from foss.arm.com ([217.140.110.172]:39432 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239981AbiBBP6Z (ORCPT ); Wed, 2 Feb 2022 10:58:25 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4FED8113E; Wed, 2 Feb 2022 07:58:25 -0800 (PST) Received: from [192.168.122.164] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C40193F73B; Wed, 2 Feb 2022 07:58:24 -0800 (PST) Message-ID: <49447f71-bb84-8e1d-e0cb-c9e482d3459b@arm.com> Date: Wed, 2 Feb 2022 09:58:15 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH RESEND] mm: memcg: synchronize objcg lists with a dedicated spinlock Content-Language: en-US To: Roman Gushchin , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alexander Egorenkov , Waiman Long , Tejun Heo , Johannes Weiner , Shakeel Butt , cgroups@vger.kernel.org References: From: Jeremy Linton In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/1/22 16:33, Roman Gushchin wrote: > Alexander reported a circular lock dependency revealed by the mmap1 > ltp test: > LOCKDEP_CIRCULAR (suite: ltp, case: mtest06 (mmap1)) > WARNING: possible circular locking dependency detected > 5.17.0-20220113.rc0.git0.f2211f194038.300.fc35.s390x+debug #1 Not tainted > ------------------------------------------------------ > mmap1/202299 is trying to acquire lock: > 00000001892c0188 (css_set_lock){..-.}-{2:2}, at: obj_cgroup_release+0x4a/0xe0 > but task is already holding lock: > 00000000ca3b3818 (&sighand->siglock){-.-.}-{2:2}, at: force_sig_info_to_task+0x38/0x180 > which lock already depends on the new lock. > the existing dependency chain (in reverse order) is: > -> #1 (&sighand->siglock){-.-.}-{2:2}: > __lock_acquire+0x604/0xbd8 > lock_acquire.part.0+0xe2/0x238 > lock_acquire+0xb0/0x200 > _raw_spin_lock_irqsave+0x6a/0xd8 > __lock_task_sighand+0x90/0x190 > cgroup_freeze_task+0x2e/0x90 > cgroup_migrate_execute+0x11c/0x608 > cgroup_update_dfl_csses+0x246/0x270 > cgroup_subtree_control_write+0x238/0x518 > kernfs_fop_write_iter+0x13e/0x1e0 > new_sync_write+0x100/0x190 > vfs_write+0x22c/0x2d8 > ksys_write+0x6c/0xf8 > __do_syscall+0x1da/0x208 > system_call+0x82/0xb0 > -> #0 (css_set_lock){..-.}-{2:2}: > check_prev_add+0xe0/0xed8 > validate_chain+0x736/0xb20 > __lock_acquire+0x604/0xbd8 > lock_acquire.part.0+0xe2/0x238 > lock_acquire+0xb0/0x200 > _raw_spin_lock_irqsave+0x6a/0xd8 > obj_cgroup_release+0x4a/0xe0 > percpu_ref_put_many.constprop.0+0x150/0x168 > drain_obj_stock+0x94/0xe8 > refill_obj_stock+0x94/0x278 > obj_cgroup_charge+0x164/0x1d8 > kmem_cache_alloc+0xac/0x528 > __sigqueue_alloc+0x150/0x308 > __send_signal+0x260/0x550 > send_signal+0x7e/0x348 > force_sig_info_to_task+0x104/0x180 > force_sig_fault+0x48/0x58 > __do_pgm_check+0x120/0x1f0 > pgm_check_handler+0x11e/0x180 > other info that might help us debug this: > Possible unsafe locking scenario: > CPU0 CPU1 > ---- ---- > lock(&sighand->siglock); > lock(css_set_lock); > lock(&sighand->siglock); > lock(css_set_lock); > *** DEADLOCK *** > 2 locks held by mmap1/202299: > #0: 00000000ca3b3818 (&sighand->siglock){-.-.}-{2:2}, at: force_sig_info_to_task+0x38/0x180 > #1: 00000001892ad560 (rcu_read_lock){....}-{1:2}, at: percpu_ref_put_many.constprop.0+0x0/0x168 > stack backtrace: > CPU: 15 PID: 202299 Comm: mmap1 Not tainted 5.17.0-20220113.rc0.git0.f2211f194038.300.fc35.s390x+debug #1 > Hardware name: IBM 3906 M04 704 (LPAR) > Call Trace: > [<00000001888aacfe>] dump_stack_lvl+0x76/0x98 > [<0000000187c6d7be>] check_noncircular+0x136/0x158 > [<0000000187c6e888>] check_prev_add+0xe0/0xed8 > [<0000000187c6fdb6>] validate_chain+0x736/0xb20 > [<0000000187c71e54>] __lock_acquire+0x604/0xbd8 > [<0000000187c7301a>] lock_acquire.part.0+0xe2/0x238 > [<0000000187c73220>] lock_acquire+0xb0/0x200 > [<00000001888bf9aa>] _raw_spin_lock_irqsave+0x6a/0xd8 > [<0000000187ef6862>] obj_cgroup_release+0x4a/0xe0 > [<0000000187ef6498>] percpu_ref_put_many.constprop.0+0x150/0x168 > [<0000000187ef9674>] drain_obj_stock+0x94/0xe8 > [<0000000187efa464>] refill_obj_stock+0x94/0x278 > [<0000000187eff55c>] obj_cgroup_charge+0x164/0x1d8 > [<0000000187ed8aa4>] kmem_cache_alloc+0xac/0x528 > [<0000000187bf2eb8>] __sigqueue_alloc+0x150/0x308 > [<0000000187bf4210>] __send_signal+0x260/0x550 > [<0000000187bf5f06>] send_signal+0x7e/0x348 > [<0000000187bf7274>] force_sig_info_to_task+0x104/0x180 > [<0000000187bf7758>] force_sig_fault+0x48/0x58 > [<00000001888ae160>] __do_pgm_check+0x120/0x1f0 > [<00000001888c0cde>] pgm_check_handler+0x11e/0x180 > INFO: lockdep is turned off. > > In this example a slab allocation from __send_signal() caused a > refilling and draining of a percpu objcg stock, resulted in a > releasing of another non-related objcg. Objcg release path requires > taking the css_set_lock, which is used to synchronize objcg lists. > > This can create a circular dependency with the sighandler lock, > which is taken with the locked css_set_lock by the freezer code > (to freeze a task). > > In general it seems that using css_set_lock to synchronize objcg lists > makes any slab allocations and deallocation with the locked > css_set_lock and any intervened locks risky. > > To fix the problem and make the code more robust let's stop using > css_set_lock to synchronize objcg lists and use a new dedicated > spinlock instead. > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > Signed-off-by: Roman Gushchin > Reported-by: Alexander Egorenkov > Tested-by: Alexander Egorenkov > Reviewed-by: Waiman Long > Cc: Tejun Heo > Cc: Johannes Weiner > Cc: Shakeel Butt > Cc: Jeremy Linton > Cc: cgroups@vger.kernel.org > --- > include/linux/memcontrol.h | 5 +++-- > mm/memcontrol.c | 10 +++++----- > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index b72d75141e12..0abbd685703b 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -219,7 +219,7 @@ struct obj_cgroup { > struct mem_cgroup *memcg; > atomic_t nr_charged_bytes; > union { > - struct list_head list; > + struct list_head list; /* protected by objcg_lock */ > struct rcu_head rcu; > }; > }; > @@ -315,7 +315,8 @@ struct mem_cgroup { > #ifdef CONFIG_MEMCG_KMEM > int kmemcg_id; > struct obj_cgroup __rcu *objcg; > - struct list_head objcg_list; /* list of inherited objcgs */ > + /* list of inherited objcgs, protected by objcg_lock */ > + struct list_head objcg_list; > #endif > > MEMCG_PADDING(_pad2_); > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 09d342c7cbd0..36e9f38c919d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -254,7 +254,7 @@ struct mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr) > } > > #ifdef CONFIG_MEMCG_KMEM > -extern spinlock_t css_set_lock; > +static DEFINE_SPINLOCK(objcg_lock); > > bool mem_cgroup_kmem_disabled(void) > { > @@ -298,9 +298,9 @@ static void obj_cgroup_release(struct percpu_ref *ref) > if (nr_pages) > obj_cgroup_uncharge_pages(objcg, nr_pages); > > - spin_lock_irqsave(&css_set_lock, flags); > + spin_lock_irqsave(&objcg_lock, flags); > list_del(&objcg->list); > - spin_unlock_irqrestore(&css_set_lock, flags); > + spin_unlock_irqrestore(&objcg_lock, flags); > > percpu_ref_exit(ref); > kfree_rcu(objcg, rcu); > @@ -332,7 +332,7 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg, > > objcg = rcu_replace_pointer(memcg->objcg, NULL, true); > > - spin_lock_irq(&css_set_lock); > + spin_lock_irq(&objcg_lock); > > /* 1) Ready to reparent active objcg. */ > list_add(&objcg->list, &memcg->objcg_list); > @@ -342,7 +342,7 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg, > /* 3) Move already reparented objcgs to the parent's list */ > list_splice(&memcg->objcg_list, &parent->objcg_list); > > - spin_unlock_irq(&css_set_lock); > + spin_unlock_irq(&objcg_lock); > > percpu_ref_kill(&objcg->refcnt); > } > Thanks for taking care of this. Since it looks the same as my patch aside from the fact that I also defensivly converted the list_del to a list_del_rcu. Reviewed-by: Jeremy Linton and Tested-by: Jeremy Linton Thanks again, From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Linton Subject: Re: [PATCH RESEND] mm: memcg: synchronize objcg lists with a dedicated spinlock Date: Wed, 2 Feb 2022 09:58:15 -0600 Message-ID: <49447f71-bb84-8e1d-e0cb-c9e482d3459b@arm.com> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Content-Language: en-US In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Roman Gushchin , Andrew Morton Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alexander Egorenkov , Waiman Long , Tejun Heo , Johannes Weiner , Shakeel Butt , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On 2/1/22 16:33, Roman Gushchin wrote: > Alexander reported a circular lock dependency revealed by the mmap1 > ltp test: > LOCKDEP_CIRCULAR (suite: ltp, case: mtest06 (mmap1)) > WARNING: possible circular locking dependency detected > 5.17.0-20220113.rc0.git0.f2211f194038.300.fc35.s390x+debug #1 Not tainted > ------------------------------------------------------ > mmap1/202299 is trying to acquire lock: > 00000001892c0188 (css_set_lock){..-.}-{2:2}, at: obj_cgroup_release+0x4a/0xe0 > but task is already holding lock: > 00000000ca3b3818 (&sighand->siglock){-.-.}-{2:2}, at: force_sig_info_to_task+0x38/0x180 > which lock already depends on the new lock. > the existing dependency chain (in reverse order) is: > -> #1 (&sighand->siglock){-.-.}-{2:2}: > __lock_acquire+0x604/0xbd8 > lock_acquire.part.0+0xe2/0x238 > lock_acquire+0xb0/0x200 > _raw_spin_lock_irqsave+0x6a/0xd8 > __lock_task_sighand+0x90/0x190 > cgroup_freeze_task+0x2e/0x90 > cgroup_migrate_execute+0x11c/0x608 > cgroup_update_dfl_csses+0x246/0x270 > cgroup_subtree_control_write+0x238/0x518 > kernfs_fop_write_iter+0x13e/0x1e0 > new_sync_write+0x100/0x190 > vfs_write+0x22c/0x2d8 > ksys_write+0x6c/0xf8 > __do_syscall+0x1da/0x208 > system_call+0x82/0xb0 > -> #0 (css_set_lock){..-.}-{2:2}: > check_prev_add+0xe0/0xed8 > validate_chain+0x736/0xb20 > __lock_acquire+0x604/0xbd8 > lock_acquire.part.0+0xe2/0x238 > lock_acquire+0xb0/0x200 > _raw_spin_lock_irqsave+0x6a/0xd8 > obj_cgroup_release+0x4a/0xe0 > percpu_ref_put_many.constprop.0+0x150/0x168 > drain_obj_stock+0x94/0xe8 > refill_obj_stock+0x94/0x278 > obj_cgroup_charge+0x164/0x1d8 > kmem_cache_alloc+0xac/0x528 > __sigqueue_alloc+0x150/0x308 > __send_signal+0x260/0x550 > send_signal+0x7e/0x348 > force_sig_info_to_task+0x104/0x180 > force_sig_fault+0x48/0x58 > __do_pgm_check+0x120/0x1f0 > pgm_check_handler+0x11e/0x180 > other info that might help us debug this: > Possible unsafe locking scenario: > CPU0 CPU1 > ---- ---- > lock(&sighand->siglock); > lock(css_set_lock); > lock(&sighand->siglock); > lock(css_set_lock); > *** DEADLOCK *** > 2 locks held by mmap1/202299: > #0: 00000000ca3b3818 (&sighand->siglock){-.-.}-{2:2}, at: force_sig_info_to_task+0x38/0x180 > #1: 00000001892ad560 (rcu_read_lock){....}-{1:2}, at: percpu_ref_put_many.constprop.0+0x0/0x168 > stack backtrace: > CPU: 15 PID: 202299 Comm: mmap1 Not tainted 5.17.0-20220113.rc0.git0.f2211f194038.300.fc35.s390x+debug #1 > Hardware name: IBM 3906 M04 704 (LPAR) > Call Trace: > [<00000001888aacfe>] dump_stack_lvl+0x76/0x98 > [<0000000187c6d7be>] check_noncircular+0x136/0x158 > [<0000000187c6e888>] check_prev_add+0xe0/0xed8 > [<0000000187c6fdb6>] validate_chain+0x736/0xb20 > [<0000000187c71e54>] __lock_acquire+0x604/0xbd8 > [<0000000187c7301a>] lock_acquire.part.0+0xe2/0x238 > [<0000000187c73220>] lock_acquire+0xb0/0x200 > [<00000001888bf9aa>] _raw_spin_lock_irqsave+0x6a/0xd8 > [<0000000187ef6862>] obj_cgroup_release+0x4a/0xe0 > [<0000000187ef6498>] percpu_ref_put_many.constprop.0+0x150/0x168 > [<0000000187ef9674>] drain_obj_stock+0x94/0xe8 > [<0000000187efa464>] refill_obj_stock+0x94/0x278 > [<0000000187eff55c>] obj_cgroup_charge+0x164/0x1d8 > [<0000000187ed8aa4>] kmem_cache_alloc+0xac/0x528 > [<0000000187bf2eb8>] __sigqueue_alloc+0x150/0x308 > [<0000000187bf4210>] __send_signal+0x260/0x550 > [<0000000187bf5f06>] send_signal+0x7e/0x348 > [<0000000187bf7274>] force_sig_info_to_task+0x104/0x180 > [<0000000187bf7758>] force_sig_fault+0x48/0x58 > [<00000001888ae160>] __do_pgm_check+0x120/0x1f0 > [<00000001888c0cde>] pgm_check_handler+0x11e/0x180 > INFO: lockdep is turned off. > > In this example a slab allocation from __send_signal() caused a > refilling and draining of a percpu objcg stock, resulted in a > releasing of another non-related objcg. Objcg release path requires > taking the css_set_lock, which is used to synchronize objcg lists. > > This can create a circular dependency with the sighandler lock, > which is taken with the locked css_set_lock by the freezer code > (to freeze a task). > > In general it seems that using css_set_lock to synchronize objcg lists > makes any slab allocations and deallocation with the locked > css_set_lock and any intervened locks risky. > > To fix the problem and make the code more robust let's stop using > css_set_lock to synchronize objcg lists and use a new dedicated > spinlock instead. > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > Signed-off-by: Roman Gushchin > Reported-by: Alexander Egorenkov > Tested-by: Alexander Egorenkov > Reviewed-by: Waiman Long > Cc: Tejun Heo > Cc: Johannes Weiner > Cc: Shakeel Butt > Cc: Jeremy Linton > Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > --- > include/linux/memcontrol.h | 5 +++-- > mm/memcontrol.c | 10 +++++----- > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index b72d75141e12..0abbd685703b 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -219,7 +219,7 @@ struct obj_cgroup { > struct mem_cgroup *memcg; > atomic_t nr_charged_bytes; > union { > - struct list_head list; > + struct list_head list; /* protected by objcg_lock */ > struct rcu_head rcu; > }; > }; > @@ -315,7 +315,8 @@ struct mem_cgroup { > #ifdef CONFIG_MEMCG_KMEM > int kmemcg_id; > struct obj_cgroup __rcu *objcg; > - struct list_head objcg_list; /* list of inherited objcgs */ > + /* list of inherited objcgs, protected by objcg_lock */ > + struct list_head objcg_list; > #endif > > MEMCG_PADDING(_pad2_); > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 09d342c7cbd0..36e9f38c919d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -254,7 +254,7 @@ struct mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr) > } > > #ifdef CONFIG_MEMCG_KMEM > -extern spinlock_t css_set_lock; > +static DEFINE_SPINLOCK(objcg_lock); > > bool mem_cgroup_kmem_disabled(void) > { > @@ -298,9 +298,9 @@ static void obj_cgroup_release(struct percpu_ref *ref) > if (nr_pages) > obj_cgroup_uncharge_pages(objcg, nr_pages); > > - spin_lock_irqsave(&css_set_lock, flags); > + spin_lock_irqsave(&objcg_lock, flags); > list_del(&objcg->list); > - spin_unlock_irqrestore(&css_set_lock, flags); > + spin_unlock_irqrestore(&objcg_lock, flags); > > percpu_ref_exit(ref); > kfree_rcu(objcg, rcu); > @@ -332,7 +332,7 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg, > > objcg = rcu_replace_pointer(memcg->objcg, NULL, true); > > - spin_lock_irq(&css_set_lock); > + spin_lock_irq(&objcg_lock); > > /* 1) Ready to reparent active objcg. */ > list_add(&objcg->list, &memcg->objcg_list); > @@ -342,7 +342,7 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg, > /* 3) Move already reparented objcgs to the parent's list */ > list_splice(&memcg->objcg_list, &parent->objcg_list); > > - spin_unlock_irq(&css_set_lock); > + spin_unlock_irq(&objcg_lock); > > percpu_ref_kill(&objcg->refcnt); > } > Thanks for taking care of this. Since it looks the same as my patch aside from the fact that I also defensivly converted the list_del to a list_del_rcu. Reviewed-by: Jeremy Linton and Tested-by: Jeremy Linton Thanks again,