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Message-ID: <CAFv23Qn=c_EZNPxu90s0n-HB6_vQCqaUG34YAq7-T6Np+10ZUA@mail.gmail.com>
Date: Tue, 10 Aug 2021 09:57:57 +0800
From: AceLan Kao <acelan.kao@...onical.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Daniel Borkmann <daniel@...earbox.net>,
Antoine Tenart <atenart@...nel.org>,
Alexander Lobakin <alobakin@...me>,
Wei Wang <weiwan@...gle.com>, Taehee Yoo <ap420073@...il.com>,
Björn Töpel <bjorn@...nel.org>,
Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [RESEND][PATCH] net: called rtnl_unlock() before runpm resumes devices
Leon Romanovsky <leon@...nel.org> 於 2021年8月9日 週一 下午1:51寫道：
>
> On Mon, Aug 09, 2021 at 11:28:09AM +0800, AceLan Kao wrote:
> > From: "Chia-Lin Kao (AceLan)" <acelan.kao@...onical.com>
> >
> > The rtnl_lock() has been called in rtnetlink_rcv_msg(), and then in
> > __dev_open() it calls pm_runtime_resume() to resume devices, and in
> > some devices' resume function(igb_resum,igc_resume) they calls rtnl_lock()
> > again. That leads to a recursive lock.
> >
> > It should leave the devices' resume function to decide if they need to
> > call rtnl_lock()/rtnl_unlock(),
>
> Why? It doesn't sound right that drivers internally decide if to take or
> release some external to them lock without seeing full picture.
>From what I observed, this is the only calling path that acquired
rtnl_lock() before calling drivers' resume function.
So, it encounters recursive lock while driver is going to cal rtnl_lock() again.
>
> Most of the time, device driver authors do it wrong. I afraid that igs
> is one of such drivers that did it wrong.
The issues could be if we remove rtnl_lock in device drivers, then in
other calling path, it won't be protected by the rtnl lock,
and maybe we shouldn't call pm_runtime_resume() here(within rtnl
lock), for device drivers don't know if they are protected by the rtnl
lock while their resume() got called.
>
> Thanks
>
> > so call rtnl_unlock() before calling pm_runtime_resume() and then call
> > rtnl_lock() after it in __dev_open().
> >
> > [ 967.723577] INFO: task ip:6024 blocked for more than 120 seconds.
> > [ 967.723588] Not tainted 5.12.0-rc3+ #1
> > [ 967.723592] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > [ 967.723594] task:ip state:D stack: 0 pid: 6024 ppid: 5957 flags:0x00004000
> > [ 967.723603] Call Trace:
> > [ 967.723610] __schedule+0x2de/0x890
> > [ 967.723623] schedule+0x4f/0xc0
> > [ 967.723629] schedule_preempt_disabled+0xe/0x10
> > [ 967.723636] __mutex_lock.isra.0+0x190/0x510
> > [ 967.723644] __mutex_lock_slowpath+0x13/0x20
> > [ 967.723651] mutex_lock+0x32/0x40
> > [ 967.723657] rtnl_lock+0x15/0x20
> > [ 967.723665] igb_resume+0xee/0x1d0 [igb]
> > [ 967.723687] ? pci_pm_default_resume+0x30/0x30
> > [ 967.723696] igb_runtime_resume+0xe/0x10 [igb]
> > [ 967.723713] pci_pm_runtime_resume+0x74/0x90
> > [ 967.723718] __rpm_callback+0x53/0x1c0
> > [ 967.723725] rpm_callback+0x57/0x80
> > [ 967.723730] ? pci_pm_default_resume+0x30/0x30
> > [ 967.723735] rpm_resume+0x547/0x760
> > [ 967.723740] __pm_runtime_resume+0x52/0x80
> > [ 967.723745] __dev_open+0x56/0x160
> > [ 967.723753] ? _raw_spin_unlock_bh+0x1e/0x20
> > [ 967.723758] __dev_change_flags+0x188/0x1e0
> > [ 967.723766] dev_change_flags+0x26/0x60
> > [ 967.723773] do_setlink+0x723/0x10b0
> > [ 967.723782] ? __nla_validate_parse+0x5b/0xb80
> > [ 967.723792] __rtnl_newlink+0x594/0xa00
> > [ 967.723800] ? nla_put_ifalias+0x38/0xa0
> > [ 967.723807] ? __nla_reserve+0x41/0x50
> > [ 967.723813] ? __nla_reserve+0x41/0x50
> > [ 967.723818] ? __kmalloc_node_track_caller+0x49b/0x4d0
> > [ 967.723824] ? pskb_expand_head+0x75/0x310
> > [ 967.723830] ? nla_reserve+0x28/0x30
> > [ 967.723835] ? skb_free_head+0x25/0x30
> > [ 967.723843] ? security_sock_rcv_skb+0x2f/0x50
> > [ 967.723850] ? netlink_deliver_tap+0x3d/0x210
> > [ 967.723859] ? sk_filter_trim_cap+0xc1/0x230
> > [ 967.723863] ? skb_queue_tail+0x43/0x50
> > [ 967.723870] ? sock_def_readable+0x4b/0x80
> > [ 967.723876] ? __netlink_sendskb+0x42/0x50
> > [ 967.723888] ? security_capable+0x3d/0x60
> > [ 967.723894] ? __cond_resched+0x19/0x30
> > [ 967.723900] ? kmem_cache_alloc_trace+0x390/0x440
> > [ 967.723906] rtnl_newlink+0x49/0x70
> > [ 967.723913] rtnetlink_rcv_msg+0x13c/0x370
> > [ 967.723920] ? _copy_to_iter+0xa0/0x460
> > [ 967.723927] ? rtnl_calcit.isra.0+0x130/0x130
> > [ 967.723934] netlink_rcv_skb+0x55/0x100
> > [ 967.723939] rtnetlink_rcv+0x15/0x20
> > [ 967.723944] netlink_unicast+0x1a8/0x250
> > [ 967.723949] netlink_sendmsg+0x233/0x460
> > [ 967.723954] sock_sendmsg+0x65/0x70
> > [ 967.723958] ____sys_sendmsg+0x218/0x290
> > [ 967.723961] ? copy_msghdr_from_user+0x5c/0x90
> > [ 967.723966] ? lru_cache_add_inactive_or_unevictable+0x27/0xb0
> > [ 967.723974] ___sys_sendmsg+0x81/0xc0
> > [ 967.723980] ? __mod_memcg_lruvec_state+0x22/0xe0
> > [ 967.723987] ? kmem_cache_free+0x244/0x420
> > [ 967.723991] ? dentry_free+0x37/0x70
> > [ 967.723996] ? mntput_no_expire+0x4c/0x260
> > [ 967.724001] ? __cond_resched+0x19/0x30
> > [ 967.724007] ? security_file_free+0x54/0x60
> > [ 967.724013] ? call_rcu+0xa4/0x250
> > [ 967.724021] __sys_sendmsg+0x62/0xb0
> > [ 967.724026] ? exit_to_user_mode_prepare+0x3d/0x1a0
> > [ 967.724032] __x64_sys_sendmsg+0x1f/0x30
> > [ 967.724037] do_syscall_64+0x38/0x90
> > [ 967.724044] entry_SYSCALL_64_after_hwframe+0x44/0xae
> >
> > Fixes: bd869245a3dc ("net: core: try to runtime-resume detached device in __dev_open")
> > Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@...onical.com>
> > ---
> > net/core/dev.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 8f1a47ad6781..dd43a29419fd 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -1585,8 +1585,11 @@ static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack)
> >
> > if (!netif_device_present(dev)) {
> > /* may be detached because parent is runtime-suspended */
> > - if (dev->dev.parent)
> > + if (dev->dev.parent) {
> > + rtnl_unlock();
> > pm_runtime_resume(dev->dev.parent);
> > + rtnl_lock();
> > + }
> > if (!netif_device_present(dev))
> > return -ENODEV;
> > }
> > --
> > 2.25.1
> >
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