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Message-ID: <1569424727.5576.221.camel@lca.pw>
Subject: Re: [PATCH] mm/slub: fix a deadlock in shuffle_freelist()
From: Qian Cai <cai@lca.pw>
To: Peter Zijlstra <peterz@infradead.org>
Cc: akpm@linux-foundation.org, bigeasy@linutronix.de, tglx@linutronix.de, 
 thgarnie@google.com, tytso@mit.edu, cl@linux.com, penberg@kernel.org, 
 rientjes@google.com, mingo@redhat.com, will@kernel.org, linux-mm@kvack.org,
  linux-kernel@vger.kernel.org, keescook@chromium.org
Date: Wed, 25 Sep 2019 11:18:47 -0400
In-Reply-To: <20190925093153.GC4553@hirez.programming.kicks-ass.net>
References: <1568392064-3052-1-git-send-email-cai@lca.pw>
	 <20190925093153.GC4553@hirez.programming.kicks-ass.net>
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On Wed, 2019-09-25 at 11:31 +0200, Peter Zijlstra wrote:
> On Fri, Sep 13, 2019 at 12:27:44PM -0400, Qian Cai wrote:
> > The commit b7d5dc21072c ("random: add a spinlock_t to struct
> > batched_entropy") insists on acquiring "batched_entropy_u32.lock" in
> > get_random_u32() which introduced the lock chain,
> >=20
> > "&rq->lock --> batched_entropy_u32.lock"
> >=20
> > even after crng init. As the result, it could result in deadlock belo=
w.
> > Fix it by using get_random_bytes() in shuffle_freelist() which does n=
ot
> > need to take on the batched_entropy locks.
> >=20
> > WARNING: possible circular locking dependency detected
> > 5.3.0-rc7-mm1+ #3 Tainted: G             L
> > ------------------------------------------------------
> > make/7937 is trying to acquire lock:
> > ffff900012f225f8 (random_write_wait.lock){....}, at:
> > __wake_up_common_lock+0xa8/0x11c
> >=20
> > but task is already holding lock:
> > ffff0096b9429c00 (batched_entropy_u32.lock){-.-.}, at:
> > get_random_u32+0x6c/0x1dc
> >=20
> > which lock already depends on the new lock.
> >=20
> > the existing dependency chain (in reverse order) is:
> >=20
> > -> #3 (batched_entropy_u32.lock){-.-.}:
> >        lock_acquire+0x31c/0x360
> >        _raw_spin_lock_irqsave+0x7c/0x9c
> >        get_random_u32+0x6c/0x1dc
> >        new_slab+0x234/0x6c0
> >        ___slab_alloc+0x3c8/0x650
> >        kmem_cache_alloc+0x4b0/0x590
> >        __debug_object_init+0x778/0x8b4
> >        debug_object_init+0x40/0x50
> >        debug_init+0x30/0x29c
> >        hrtimer_init+0x30/0x50
> >        init_dl_task_timer+0x24/0x44
> >        __sched_fork+0xc0/0x168
> >        init_idle+0x78/0x26c
> >        fork_idle+0x12c/0x178
> >        idle_threads_init+0x108/0x178
> >        smp_init+0x20/0x1bc
> >        kernel_init_freeable+0x198/0x26c
> >        kernel_init+0x18/0x334
> >        ret_from_fork+0x10/0x18
> >=20
> > -> #2 (&rq->lock){-.-.}:
>=20
> This relation is silly..
>=20
> I suspect the below 'works'...

Unfortunately, the relation is still there,

copy_process()->rt_mutex_init_task()->"&p->pi_lock"

[24438.676716][=C2=A0=C2=A0=C2=A0=C2=A0T2] -> #2 (&rq->lock){-.-.}:
[24438.676727][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__lock_acquire+0x5b4/0xbf0
[24438.676736][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0lock_acquire+0x130/0x360
[24438.676754][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_raw_spin_lock+0x54/0x80
[24438.676771][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0task_fork_fair+0x60/0x190
[24438.676788][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0sched_fork+0x128/0x270
[24438.676806][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0copy_process+0x7a4/0x1bf0
[24438.676823][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_do_fork+0xac/0xac0
[24438.676841][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kernel_thread+0x70/0xa0
[24438.676858][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0rest_init+0x4c/0x42c
[24438.676884][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0start_kernel+0x778/0x7c0
[24438.676902][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0start_here_common+0x1c/0x334

Whole thing,

[24438.675704][=C2=A0=C2=A0=C2=A0=C2=A0T2] WARNING: possible circular loc=
king dependency detected
[24438.675714][=C2=A0=C2=A0=C2=A0=C2=A0T2] 5.3.0-next-20190924 #2 Not tai=
nted
[24438.675722][=C2=A0=C2=A0=C2=A0=C2=A0T2] ------------------------------=
------------------------
[24438.675731][=C2=A0=C2=A0=C2=A0=C2=A0T2] kthreadd/2 is trying to acquir=
e lock:
[24438.675740][=C2=A0=C2=A0=C2=A0=C2=A0T2] c0000000010a7450 (random_write=
_wait.lock){..-.}, at:
__wake_up_common_lock+0x88/0x110
[24438.675768][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.675768][=C2=A0=C2=A0=C2=A0=C2=A0T2] but task is already holding lo=
ck:
[24438.675778][=C2=A0=C2=A0=C2=A0=C2=A0T2] c000001ffd2f06e0 (batched_entr=
opy_u64.lock){-...}, at:
get_random_u64+0x60/0x100
[24438.675803][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.675803][=C2=A0=C2=A0=C2=A0=C2=A0T2] which lock already depends on =
the new lock.
[24438.675803][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.675816][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.675816][=C2=A0=C2=A0=C2=A0=C2=A0T2] the existing dependency chain =
(in reverse order) is:
[24438.675836][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.675836][=C2=A0=C2=A0=C2=A0=C2=A0T2] -> #4 (batched_entropy_u64.loc=
k){-...}:
[24438.675860][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__lock_acquire+0x5b4/0xbf0
[24438.675878][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0lock_acquire+0x130/0x360
[24438.675906][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_raw_spin_lock_irqsave+0x70/0xa0
[24438.675923][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0get_random_u64+0x60/0x100
[24438.675944][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0add_to_free_area_random+0x164/0x1b0
[24438.675962][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0free_one_page+0xb24/0xcf0
[24438.675980][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__free_pages_ok+0x448/0xbf0
[24438.675999][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0deferred_init_maxorder+0x404/0x4a4
[24438.676018][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0deferred_grow_zone+0x158/0x1f0
[24438.676035][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0get_page_from_freelist+0x1dc8/0x1e10
[24438.676063][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__alloc_pages_nodemask+0x1d8/0x1940
[24438.676083][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0allocate_slab+0x130/0x2740
[24438.676091][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0new_slab+0xa8/0xe0
[24438.676101][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kmem_cache_open+0x254/0x660
[24438.676119][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__kmem_cache_create+0x44/0x2a0
[24438.676136][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0create_boot_cache+0xcc/0x110
[24438.676154][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kmem_cache_init+0x90/0x1f0
[24438.676173][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0start_kernel+0x3b8/0x7c0
[24438.676191][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0start_here_common+0x1c/0x334
[24438.676208][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.676208][=C2=A0=C2=A0=C2=A0=C2=A0T2] -> #3 (&(&zone->lock)->rlock){=
-.-.}:
[24438.676221][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__lock_acquire+0x5b4/0xbf0
[24438.676247][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0lock_acquire+0x130/0x360
[24438.676264][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_raw_spin_lock+0x54/0x80
[24438.676282][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0rmqueue_bulk.constprop.23+0x64/0xf20
[24438.676300][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0get_page_from_freelist+0x718/0x1e10
[24438.676319][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__alloc_pages_nodemask+0x1d8/0x1940
[24438.676339][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0alloc_page_interleave+0x34/0x170
[24438.676356][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0allocate_slab+0xd1c/0x2740
[24438.676374][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0new_slab+0xa8/0xe0
[24438.676391][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0___slab_alloc+0x580/0xef0
[24438.676408][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__slab_alloc+0x64/0xd0
[24438.676426][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kmem_cache_alloc+0x5c4/0x6c0
[24438.676444][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0fill_pool+0x280/0x540
[24438.676461][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__debug_object_init+0x60/0x6b0
[24438.676479][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0hrtimer_init+0x5c/0x310
[24438.676497][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0init_dl_task_timer+0x34/0x60
[24438.676516][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__sched_fork+0x8c/0x110
[24438.676535][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0init_idle+0xb4/0x3c0
[24438.676553][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0idle_thread_get+0x78/0x120
[24438.676572][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0bringup_cpu+0x30/0x230
[24438.676590][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0cpuhp_invoke_callback+0x190/0x1580
[24438.676618][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0do_cpu_up+0x248/0x460
[24438.676636][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0smp_init+0x118/0x1c0
[24438.676662][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kernel_init_freeable+0x3f8/0x8dc
[24438.676681][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kernel_init+0x2c/0x154
[24438.676699][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0ret_from_kernel_thread+0x5c/0x74
[24438.676716][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.676716][=C2=A0=C2=A0=C2=A0=C2=A0T2] -> #2 (&rq->lock){-.-.}:
[24438.676727][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__lock_acquire+0x5b4/0xbf0
[24438.676736][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0lock_acquire+0x130/0x360
[24438.676754][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_raw_spin_lock+0x54/0x80
[24438.676771][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0task_fork_fair+0x60/0x190
[24438.676788][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0sched_fork+0x128/0x270
[24438.676806][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0copy_process+0x7a4/0x1bf0
[24438.676823][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_do_fork+0xac/0xac0
[24438.676841][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kernel_thread+0x70/0xa0
[24438.676858][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0rest_init+0x4c/0x42c
[24438.676884][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0start_kernel+0x778/0x7c0
[24438.676902][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0start_here_common+0x1c/0x334
[24438.676910][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.676910][=C2=A0=C2=A0=C2=A0=C2=A0T2] -> #1 (&p->pi_lock){-.-.}:
[24438.676921][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__lock_acquire+0x5b4/0xbf0
[24438.676929][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0lock_acquire+0x130/0x360
[24438.676947][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_raw_spin_lock_irqsave+0x70/0xa0
[24438.676973][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0try_to_wake_up+0x70/0x1600
[24438.676991][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0pollwake+0x88/0xc0
[24438.677009][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__wake_up_common+0xec/0x280
[24438.677026][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__wake_up_common_lock+0xac/0x110
[24438.677044][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0account.constprop.8+0x284/0x430
[24438.677061][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0extract_entropy.constprop.7+0xd4/0x330
[24438.677080][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_xfer_secondary_pool+0x104/0x3e0
[24438.677097][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0push_to_pool+0x58/0x310
[24438.677116][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0process_one_work+0x300/0x8e0
[24438.677133][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0worker_thread+0x78/0x530
[24438.677151][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kthread+0x1a8/0x1b0
[24438.677180][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0ret_from_kernel_thread+0x5c/0x74
[24438.677245][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.677245][=C2=A0=C2=A0=C2=A0=C2=A0T2] -> #0 (random_write_wait.lock)=
{..-.}:
[24438.677329][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0check_prev_add+0x100/0x11b0
[24438.677377][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0validate_chain+0x868/0x1530
[24438.677446][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__lock_acquire+0x5b4/0xbf0
[24438.677516][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0lock_acquire+0x130/0x360
[24438.677563][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_raw_spin_lock_irqsave+0x70/0xa0
[24438.677618][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0__wake_up_common_lock+0x88/0x110
[24438.677678][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0account.constprop.8+0x284/0x430
[24438.677743][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0extract_entropy.constprop.7+0xd4/0x330
[24438.677802][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0crng_reseed+0x68/0x490
[24438.677867][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_extract_crng+0x104/0x110
[24438.677914][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0crng_reseed+0x284/0x490
[24438.677983][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_extract_crng+0x104/0x110
[24438.678032][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0get_random_u64+0xdc/0x100
[24438.678101][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0copy_process+0x2d8/0x1bf0
[24438.678148][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0_do_fork+0xac/0xac0
[24438.678208][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kernel_thread+0x70/0xa0
[24438.678246][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0kthreadd+0x270/0x330
[24438.678301][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0ret_from_kernel_thread+0x5c/0x74
[24438.678342][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.678342][=C2=A0=C2=A0=C2=A0=C2=A0T2] other info that might help us =
debug this:
[24438.678342][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.678459][=C2=A0=C2=A0=C2=A0=C2=A0T2] Chain exists of:
[24438.678459][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0random_write_=
wait.lock --> &(&zone->lock)->rlock -->
batched_entropy_u64.lock
[24438.678459][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.678636][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0Possible unsafe loc=
king scenario:
[24438.678636][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.678692][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0CPU0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0CPU1
[24438.678754][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0----=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0----
[24438.678814][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0lock(batched_=
entropy_u64.lock);
[24438.678878][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0lock(&(&zone->lock)-
>rlock);
[24438.678951][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0lock(batched_entropy_u64.l
ock);
[24438.679038][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0=C2=A0lock(random_w=
rite_wait.lock);
[24438.679098][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.679098][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0*** DEADLOCK ***
[24438.679098][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.679174][=C2=A0=C2=A0=C2=A0=C2=A0T2] 1 lock held by kthreadd/2:
[24438.679230][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0=C2=A0#0: c000001ffd2f06e=
0 (batched_entropy_u64.lock){-...},
at: get_random_u64+0x60/0x100
[24438.679341][=C2=A0=C2=A0=C2=A0=C2=A0T2]=C2=A0
[24438.679341][=C2=A0=C2=A0=C2=A0=C2=A0T2] stack backtrace:
[24438.679413][=C2=A0=C2=A0=C2=A0=C2=A0T2] CPU: 13 PID: 2 Comm: kthreadd =
Not tainted 5.3.0-next-
20190924 #2
[24438.679485][=C2=A0=C2=A0=C2=A0=C2=A0T2] Call Trace:
[24438.679507][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84efe0] [c000000000=
91a574]
dump_stack+0xe8/0x164 (unreliable)
[24438.679618][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f030] [c000000000=
1cc9b8]
print_circular_bug+0x3a8/0x420
[24438.679701][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f0e0] [c000000000=
1ccc90]
check_noncircular+0x260/0x320
[24438.679769][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f1e0] [c000000000=
1ce7e0]
check_prev_add+0x100/0x11b0
[24438.679868][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f2c0] [c000000000=
1d00f8]
validate_chain+0x868/0x1530
[24438.679950][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f3f0] [c000000000=
1d3064]
__lock_acquire+0x5b4/0xbf0
[24438.680059][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f4f0] [c000000000=
1d3ed0]
lock_acquire+0x130/0x360
[24438.680122][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f5d0] [c000000000=
947d70]
_raw_spin_lock_irqsave+0x70/0xa0
[24438.680207][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f610] [c000000000=
1a9488]
__wake_up_common_lock+0x88/0x110
[24438.680298][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f690] [c000000000=
6f11a4]
account.constprop.8+0x284/0x430
[24438.680399][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f750] [c000000000=
6f1554]
extract_entropy.constprop.7+0xd4/0x330
[24438.680495][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f7d0] [c000000000=
6f1818]
crng_reseed+0x68/0x490
[24438.680590][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f910] [c000000000=
6f4094]
_extract_crng+0x104/0x110
[24438.680662][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84f950] [c000000000=
6f1a34]
crng_reseed+0x284/0x490
[24438.680751][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84fa90] [c000000000=
6f4094]
_extract_crng+0x104/0x110
[24438.680828][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84fad0] [c000000000=
6f4c0c]
get_random_u64+0xdc/0x100
[24438.680931][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84fb10] [c000000000=
106988]
copy_process+0x2d8/0x1bf0
[24438.681007][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84fc30] [c000000000=
10861c] _do_fork+0xac/0xac0
[24438.681074][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84fd10] [c000000000=
1090d0]
kernel_thread+0x70/0xa0
[24438.681170][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84fd80] [c000000000=
1518f0]
kthreadd+0x270/0x330
[24438.681257][=C2=A0=C2=A0=C2=A0=C2=A0T2] [c00000002c84fe20] [c000000000=
00b748]
ret_from_kernel_thread+0x5c/0x74

>=20
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 63900ca029e0..ec1d72f18b34 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6027,10 +6027,11 @@ void init_idle(struct task_struct *idle, int cp=
u)
>  	struct rq *rq =3D cpu_rq(cpu);
>  	unsigned long flags;
> =20
> +	__sched_fork(0, idle);
> +
>  	raw_spin_lock_irqsave(&idle->pi_lock, flags);
>  	raw_spin_lock(&rq->lock);
> =20
> -	__sched_fork(0, idle);
>  	idle->state =3D TASK_RUNNING;
>  	idle->se.exec_start =3D sched_clock();
>  	idle->flags |=3D PF_IDLE;