From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f181.google.com (mail-qk0-f181.google.com [209.85.220.181]) by kanga.kvack.org (Postfix) with ESMTP id 701276B0073 for ; Tue, 26 May 2015 09:56:27 -0400 (EDT) Received: by qkdn188 with SMTP id n188so89296814qkd.2 for ; Tue, 26 May 2015 06:56:27 -0700 (PDT) Received: from mail-qg0-f52.google.com (mail-qg0-f52.google.com. [209.85.192.52]) by mx.google.com with ESMTPS id 74si11723989qhq.106.2015.05.26.06.56.25 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 May 2015 06:56:26 -0700 (PDT) Received: by qgg60 with SMTP id 60so10315080qgg.2 for ; Tue, 26 May 2015 06:56:25 -0700 (PDT) Date: Tue, 26 May 2015 09:56:14 -0400 From: Jeff Layton Subject: Re: swap: nfs: Sleeping function called from an rcu read section in nfs_swap_activate Message-ID: <20150526095614.5b3d0e84@synchrony.poochiereds.net> In-Reply-To: <5564732E.4090607@redhat.com> References: <5564732E.4090607@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/FWG1iURMp0MKzwwv0luehxu"; protocol="application/pgp-signature" Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Marchand Cc: Mel Gorman , Jeff Layton , 'Linux-MM' , 'linux-kernel' --Sig_/FWG1iURMp0MKzwwv0luehxu Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 26 May 2015 15:20:46 +0200 Jerome Marchand wrote: >=20 > Commit dad2b015 added an rcu read lock around the call to xs_swapper() > in nfs_activate()/deactivate(), which can sleep, thus raising a bug at > each swapon and swapoff over NFS. > I'm not sure if this is related or not, but swapoff also triggers the > WARN_ON(sk->sk_forward_alloc) in sk_clear_memalloc(). >=20 > [ 243.668067] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > [ 243.668665] [ INFO: suspicious RCU usage. ] > [ 243.669293] 4.1.0-rc1-lock_stat-dbg-next-20150430+ #235 Not tainted > [ 243.670301] ------------------------------- > [ 243.670905] include/linux/rcupdate.h:570 Illegal context switch in RCU= read-side critical section! > [ 243.672163]=20 > other info that might help us debug this: >=20 > [ 243.673025]=20 > rcu_scheduler_active =3D 1, debug_locks =3D 0 > [ 243.673565] 2 locks held by swapon/1176: > [ 243.673893] #0: (&sb->s_type->i_mutex_key#17){+.+.+.}, at: [] SyS_swapon+0x2b0/0x1000 > [ 243.674758] #1: (rcu_read_lock){......}, at: [] nf= s_swap_activate+0x5/0x180 [nfs] > [ 243.675591]=20 > stack backtrace: > [ 243.675957] CPU: 0 PID: 1176 Comm: swapon Not tainted 4.1.0-rc1-lock_s= tat-dbg-next-20150430+ #235 > [ 243.676687] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 243.677179] 0000000000000000 00000000ef88d841 ffff88003327bcd8 ffffff= ff818861f0 > [ 243.677854] 0000000000000000 ffff880078e38000 ffff88003327bd08 ffffff= ff8110d237 > [ 243.678514] 0000000000000000 ffffffff81c650e4 0000000000000268 ffff88= 0078e38000 > [ 243.679171] Call Trace: > [ 243.679383] [] dump_stack+0x4c/0x65 > [ 243.679811] [] lockdep_rcu_suspicious+0xe7/0x120 > [ 243.680348] [] ___might_sleep+0xaf/0x250 > [ 243.680815] [] __might_sleep+0x4d/0x90 > [ 243.681279] [] mutex_lock_nested+0x47/0x430 > [ 243.681762] [] static_key_slow_inc+0x7c/0xc0 > [ 243.682264] [] sk_set_memalloc+0x27/0x30 > [ 243.682736] [] xs_swapper+0x54/0x60 [sunrpc] > [ 243.683238] [] nfs_swap_activate+0x93/0x180 [nfs] > [ 243.683760] [] ? nfs_swap_activate+0x5/0x180 [nfs] > [ 243.684316] [] SyS_swapon+0xad4/0x1000 > [ 243.684766] [] ? syscall_return+0x16/0x59 > [ 243.685245] [] system_call_fastpath+0x12/0x76 > [ 243.685743] BUG: sleeping function called from invalid context at kern= el/locking/mutex.c:616 > [ 243.686439] in_atomic(): 1, irqs_disabled(): 0, pid: 1176, name: swapon > [ 243.687053] INFO: lockdep is turned off. > [ 243.687429] CPU: 0 PID: 1176 Comm: swapon Not tainted 4.1.0-rc1-lock_s= tat-dbg-next-20150430+ #235 > [ 243.688313] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 243.688845] 0000000000000000 00000000ef88d841 ffff88003327bd08 ffffff= ff818861f0 > [ 243.689570] 0000000000000000 ffff880078e38000 ffff88003327bd38 ffffff= ff810df29c > [ 243.690353] ffff880000000001 ffffffff81c650e4 0000000000000268 000000= 0000000000 > [ 243.691057] Call Trace: > [ 243.691315] [] dump_stack+0x4c/0x65 > [ 243.691785] [] ___might_sleep+0x18c/0x250 > [ 243.692306] [] __might_sleep+0x4d/0x90 > [ 243.692807] [] mutex_lock_nested+0x47/0x430 > [ 243.693346] [] static_key_slow_inc+0x7c/0xc0 > [ 243.693887] [] sk_set_memalloc+0x27/0x30 > [ 243.694416] [] xs_swapper+0x54/0x60 [sunrpc] > [ 243.694959] [] nfs_swap_activate+0x93/0x180 [nfs] > [ 243.695535] [] ? nfs_swap_activate+0x5/0x180 [nfs] > [ 243.696193] [] SyS_swapon+0xad4/0x1000 > [ 243.696699] [] ? syscall_return+0x16/0x59 > [ 243.697299] [] system_call_fastpath+0x12/0x76 > [ 243.702101] Adding 524284k swap on /mnt/swapfile512. Priority:-2 exte= nts:1 across:524284k FS > [ 325.151350] BUG: sleeping function called from invalid context at kern= el/locking/mutex.c:616 > [ 325.152688] in_atomic(): 1, irqs_disabled(): 0, pid: 1199, name: swapo= ff > [ 325.153737] INFO: lockdep is turned off. > [ 325.154457] CPU: 1 PID: 1199 Comm: swapoff Not tainted 4.1.0-rc1-lock_= stat-dbg-next-20150430+ #235 > [ 325.156204] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 325.157120] 0000000000000000 00000000a7682b83 ffff88007ac3fce8 ffffff= ff818861f0 > [ 325.158361] 0000000000000000 ffff880032434c00 ffff88007ac3fd18 ffffff= ff810df29c > [ 325.159592] 0000000000000000 ffffffff81c650e4 0000000000000268 000000= 0000000000 > [ 325.160798] Call Trace: > [ 325.161251] [] dump_stack+0x4c/0x65 > [ 325.162071] [] ___might_sleep+0x18c/0x250 > [ 325.163073] [] __might_sleep+0x4d/0x90 > [ 325.163934] [] mutex_lock_nested+0x47/0x430 > [ 325.164927] [] atomic_dec_and_mutex_lock+0x4f/0x70 > [ 325.166020] [] __static_key_slow_dec+0x27/0xc0 > [ 325.166942] [] static_key_slow_dec+0x26/0x50 > [ 325.167955] [] sk_clear_memalloc+0x2f/0x80 > [ 325.169075] [] xs_swapper+0x41/0x60 [sunrpc] > [ 325.170241] [] nfs_swap_deactivate+0x87/0x170 [nfs] > [ 325.171276] [] ? nfs_swap_deactivate+0x5/0x170 [nfs] > [ 325.172349] [] destroy_swap_extents+0x77/0x90 > [ 325.173754] [] SyS_swapoff+0x215/0x600 > [ 325.174726] [] ? trace_hardirqs_on_thunk+0x17/0x19 > [ 325.175971] [] system_call_fastpath+0x12/0x76 > [ 325.178052] ------------[ cut here ]------------ > [ 325.178892] WARNING: CPU: 1 PID: 1199 at net/core/sock.c:364 sk_clear_= memalloc+0x51/0x80() > [ 325.180363] Modules linked in: rpcsec_gss_krb5 nfsv4 dns_resolver nfs = fscache ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack ebtable_nat e= btable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntr= ack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6ta= ble_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_= ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptabl= e_raw iosf_mbi crct10dif_pclmul crc32_pclmul crc32c_intel ppdev ghash_clmul= ni_intel joydev nfsd parport_pc pcspkr virtio_console serio_raw virtio_ball= oon parport pvpanic i2c_piix4 acpi_cpufreq auth_rpcgss nfs_acl lockd grace = sunrpc virtio_blk qxl virtio_net drm_kms_helper ttm drm virtio_pci virtio_r= ing virtio ata_generic pata_acpi floppy > [ 325.192279] CPU: 1 PID: 1199 Comm: swapoff Not tainted 4.1.0-rc1-lock_= stat-dbg-next-20150430+ #235 > [ 325.193605] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 325.194491] 0000000000000000 00000000a7682b83 ffff88007ac3fdf8 ffffff= ff818861f0 > [ 325.195692] 0000000000000000 0000000000000000 ffff88007ac3fe38 ffffff= ff810af5ca > [ 325.196891] ffff88007ac3fe78 ffff88007b068000 ffff88007b484a00 ffff88= 007b484aa8 > [ 325.198119] Call Trace: > [ 325.198555] [] dump_stack+0x4c/0x65 > [ 325.199380] [] warn_slowpath_common+0x8a/0xc0 > [ 325.200601] [] warn_slowpath_null+0x1a/0x20 > [ 325.201536] [] sk_clear_memalloc+0x51/0x80 > [ 325.202468] [] xs_swapper+0x41/0x60 [sunrpc] > [ 325.203398] [] nfs_swap_deactivate+0x87/0x170 [nfs] > [ 325.204426] [] ? nfs_swap_deactivate+0x5/0x170 [nfs] > [ 325.205456] [] destroy_swap_extents+0x77/0x90 > [ 325.206406] [] SyS_swapoff+0x215/0x600 > [ 325.207287] [] ? trace_hardirqs_on_thunk+0x17/0x19 > [ 325.208300] [] system_call_fastpath+0x12/0x76 > [ 325.209248] ---[ end trace 13f1014b56e5e711 ]--- >=20 Ok. What I think we need to do here is take a reference to the cl_xprt while holding the rcu_read_lock, and simply put it after we're done. That said...what happens if this xprt is switched out from under the clnt while we're swapping over it? It seems like rpc_switch_client_transport ought to be swap deactivating the old one and swap activating the new? Mel, any thoughts?=20 --=20 Jeff Layton --Sig_/FWG1iURMp0MKzwwv0luehxu Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJVZHt/AAoJEAAOaEEZVoIVg/YP/iVt1M3c2KjdjBFAsXB5UIPj xkRGUlCmQ2NuseTm34JgrFbe+Hx3atGMTx5du8R0CY0kKRFXC5zjpdardVX47i8N /fxdh0Q6JONKduX0zzFEYuN8nGrhHZIRU14j+hRUG5MGcQ+z3Ge06GELuCVFO6Ps en0pjI/sb6MjA7AX4ClyMbs947l+3xIJVwumKrZXomOc6ejyLx6pm+6PLfge84kW sK3ftIozrxiZqMOMZ8jjQqbh+vjAkbqjEMEYWF0H8rUGD3/+7TojErGuRd8m0HWo 8inIe9wTmWXrCSypuCEMT4xweDTW07/MKy2GHS3DnT8J1+zFzY7sv2YXhioRPMM4 hLmQXckHwK+dOdMQy3FPVVlbYrjgH1Zww0gwYOG0pmSdEaiz532JdC5SiL64btbH cZ8QeP/FzUpfegQLQmEU1f6UCq14gCUGMGb2lHWdaFcGgzKaAB3bNGDeSmde1l+v xiIM37qxImc0L1YqQW36bvsqMhUbhc6TEcKZZhsAzQGUZVYWbGzW8w3TvomorK/u QI73w7eT4IK0gmB1vM8Y9WVGKhdQDSXluj1j94cstbEJP22zPvSUo/UeirIWl1jn SJ5rvuYOgdvhK2e96pb6wtO1pI4OavbabNOLHepCo97bazN42OKyrfpDQul+BtCH Mq5e97xLJXtBQsWPD7VP =D/zb -----END PGP SIGNATURE----- --Sig_/FWG1iURMp0MKzwwv0luehxu-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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