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=?us-ascii?Q?BjIZQ480do3/QSmmKPA+ocxb3gwWfDsQrFIBUAikpL9jpA+E2I4NNRYN1vTs?= =?us-ascii?Q?JAKQds60EHM6FEYjNY4IfUle88x1EXBDcpa9JuJVhV+gUFy8tH8=3D?= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Message-ID: <20191009162339.p71IUWLPzTq4eR6U4OzC1pApqqtqzqPzwZEzJewXse0@z> On Wed 09-10-19 11:08:35, Qian Cai wrote: > On Wed, 2019-10-09 at 16:34 +0200, Michal Hocko wrote: > > On Wed 09-10-19 10:19:44, Qian Cai wrote: > > > On Wed, 2019-10-09 at 15:51 +0200, Michal Hocko wrote: > >=20 > > [=2E=2E=2E] > > > > Can you paste the full lock chain graph to be sure we are on the sa= me > > > > page? > > >=20 > > > WARNING: possible circular locking dependency detected > > > 5=2E3=2E0-next-20190917 #8 Not tainted > > > ------------------------------------------------------ > > > test=2Esh/8653 is trying to acquire lock: > > > ffffffff865a4460 (console_owner){-=2E-=2E}, at: > > > console_unlock+0x207/0x750 > > >=20 > > > but task is already holding lock: > > > ffff88883fff3c58 (&(&zone->lock)->rlock){-=2E-=2E}, at: > > > __offline_isolated_pages+0x179/0x3e0 > > >=20 > > > which lock already depends on the new lock=2E > > >=20 > > >=20 > > > the existing dependency chain (in reverse order) is: > > >=20 > > > -> #3 (&(&zone->lock)->rlock){-=2E-=2E}: > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0__lock_acquire+0x5b3/0xb40 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0lock_acquire+0x126/0x280 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0_raw_spin_lock+0x2f/0x40 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0rmqueue_bulk=2Econstprop=2E2= 1+0xb6/0x1160 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0get_page_from_freelist+0x89= 8/0x22c0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0__alloc_pages_nodemask+0x2f= 3/0x1cd0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0alloc_pages_current+0x9c/0x= 110 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0allocate_slab+0x4c6/0x19c0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0new_slab+0x46/0x70 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0___slab_alloc+0x58b/0x960 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0__slab_alloc+0x43/0x70 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0__kmalloc+0x3ad/0x4b0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0__tty_buffer_request_room+0= x100/0x250 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0tty_insert_flip_string_fixe= d_flag+0x67/0x110 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0pty_write+0xa2/0xf0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0n_tty_write+0x36b/0x7b0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0tty_write+0x284/0x4c0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0__vfs_write+0x50/0xa0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0vfs_write+0x105/0x290 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0redirected_tty_write+0x6a/0= xc0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0do_iter_write+0x248/0x2a0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0vfs_writev+0x106/0x1e0 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0do_writev+0xd4/0x180 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0__x64_sys_writev+0x45/0x50 > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0do_syscall_64+0xcc/0x76c > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0entry_SYSCALL_64_after_hwfr= ame+0x49/0xbe > >=20 > > This one looks indeed legit=2E pty_write is allocating memory from insi= de > > the port->lock=2E But this seems to be quite broken, right? The forward= > > progress depends on GFP_ATOMIC allocation which might fail easily under= > > memory pressure=2E So the preferred way to fix this should be to change= > > the allocation scheme to use the preallocated buffer and size it from a= > > context when it doesn't hold internal locks=2E It might be a more compl= ex > > fix than using printk_deferred or other games but addressing that would= > > make the pty code more robust as well=2E >=20 > I am not really sure if doing a surgery in pty code is better than fixing= the > memory offline side as a short-term fix=2E If this was only about the memory offline code then I would agree=2E But we are talking about any printk from the zone->lock context and that is a bigger deal=2E Besides that it is quite natural that the printk code should be more universal and allow to be also called from the MM contexts as much as possible=2E If there is any really strong reason this is not possible then it should be documented at least=2E --=20 Michal Hocko SUSE Labs