[PATCH] bonding: minor cleanups to bond + netpoll

[PATCH] bonding: minor cleanups to bond + netpoll

[nhorman]

Testing that was onging when the the reset patchset to enable netpoll over
bonding revealed some minor corner cases that are worth correcting.  In summary:

1) Remove netpoll tx blocking from bond_release_all.  Its not needed and causes
some uglyness when removing the bonding module, in the form of a backtrace that
gets logged.  blocking isn't needed in this path anyway as the netconsole is
already unregistered from us at this point

2) Remove my changes to napi_poll.  Closer inspection of the bonding
poll_controller show that we wind up recursively calling the napi poll routines
for the slaves through sucsessive calls to netpoll_poll_dev.  My origional
change is harmless, but its not really needed, so lets make the code simpler.

Further details available in the individual commit messages

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

[PATCH 1/2] Remove netpoll blocking from uninit path

[nhorman]

From: Neil Horman <nhorman@tuxdriver.com>

Some recent testing in netpoll with bonding showed this backtrace

 ------------[ cut here ]------------
 kernel BUG at drivers/net/bonding/bonding.h:134!
 invalid opcode: 0000 [#1] SMP
 last sysfs file: /sys/devices/pci0000:00/0000:00:1d.2/usb7/devnum
 CPU 0
 Pid: 1876, comm: rmmod Not tainted 2.6.36-rc3+ #10 D26928/
 RIP: 0010:[<ffffffffa0514ba4>]  [<ffffffffa0514ba4>] bond_uninit+0x6f4/0x7a0
 RSP: 0018:ffff88003b1b5d58  EFLAGS: 00010296
 RAX: ffff88003b9b6200 RBX: ffff8800373e8e00 RCX: 00000000000f4240
 RDX: 00000000ffffffff RSI: 0000000000000286 RDI: 0000000000000286
 RBP: ffff88003b1b5dc8 R08: 0000000000000000 R09: 00000001af7de920
 R10: 0000000000000000 R11: ffff880002495e98 R12: ffff880037922700
 R13: ffff880038c31000 R14: ffff880037922730 R15: 0000000000000286
 FS:  00007f90e6d72700(0000) GS:ffff880002400000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
 CR2: 000000346f0d9ad0 CR3: 000000003b263000 CR4: 00000000000006f0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
 Process rmmod (pid: 1876, threadinfo ffff88003b1b4000, task ffff88003b36aa80)
 Stack:
 00000000ffffffff ffff88003b1b5d7a ffff8800379221e8 ffff880037922000
 <0> ffff88003b1b5dc8 ffffffff813eb5fb ffff88003b1b5da8 0000000031b177a3
 <0> ffff88003b1b5da8 ffff880037922000 ffff88003b1b5e48 ffff88003b1b5e48
 Call Trace:
 [<ffffffff813eb5fb>] ? rtmsg_ifinfo+0xcb/0xf0
 [<ffffffff813daad8>] rollback_registered_many+0x168/0x280
 [<ffffffff813dac09>] unregister_netdevice_many+0x19/0x80
 [<ffffffff813e97b3>] __rtnl_kill_links+0x63/0x90
 [<ffffffff813e980b>] __rtnl_link_unregister+0x2b/0x60
 [<ffffffff813e9bde>] rtnl_link_unregister+0x1e/0x30
 [<ffffffffa052124b>] bonding_exit+0x37/0x51 [bonding]
 [<ffffffff81098b2e>] sys_delete_module+0x19e/0x270
 [<ffffffff810bb2b2>] ? audit_syscall_entry+0x252/0x280
 [<ffffffff8100b0b2>] system_call_fastpath+0x16/0x1b
 RIP  [<ffffffffa0514ba4>] bond_uninit+0x6f4/0x7a0 [bonding]
 RSP <ffff88003b1b5d58>
 ---[ end trace 1395ad691cea24d1 ]---

It occurs because of my recent netpoll blocking patches, which I added to avoid
recursive deadlock in the bonding driver.  It relies on some per cpu bits, but
the shutdown path forces some rescheduling as we cancel workqueues for the
driver and wait for some device refcounts.  If after the forced reschedule, we
wind up on a different cpu we trigger the bughalt in unblock_netpoll_tx.

The fix is to remove the netpoll block/unblock calls from bond_release_all.
This is safe to do because bond_uninit, which is called via ndo_uninit in
rollback_registered_many, doesn't occur until we send a NETDEV_UNREGISTER event,
which triggers netconsole to remove us as a netpoll client, so we are guaranteed
not to recurse into our own tx path here.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
---
 drivers/net/bonding/bond_main.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 38d4ca0..99cb891 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2082,7 +2082,6 @@ static int bond_release_all(struct net_device *bond_dev)
 	struct net_device *slave_dev;
 	struct sockaddr addr;
 
-	block_netpoll_tx();
 	write_lock_bh(&bond->lock);
 
 	netif_carrier_off(bond_dev);
@@ -2181,8 +2180,6 @@ static int bond_release_all(struct net_device *bond_dev)
 
 out:
 	write_unlock_bh(&bond->lock);
-	unblock_netpoll_tx();
-
 	return 0;
 }
 
-- 
1.7.2.3

[PATCH 2/2] Revert napi_poll fix for bonding driver

[nhorman]

From: Neil Horman <nhorman@tuxdriver.com>

In an erlier patch I modified napi_poll so that devices with IFF_MASTER polled
the per_cpu list instead of the device list for napi.  I did this because the
bonding driver has no napi instances to poll, it instead expects to check the
slave devices napi instances, which napi_poll was unaware of.  Looking at this
more closely however, I now see this isn't strictly needed.  As the bond driver
poll_controller calls the slaves poll_controller via netpoll_poll_dev, which
recursively calls poll_napi on each slave, allowing those napi instances to get
serviced.  The earlier patch isn't at all harmfull, its just not needed, so lets
revert it to make the code cleaner.  Sorry for the noise,

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
---
 net/core/netpoll.c |    9 +--------
 1 files changed, 1 insertions(+), 8 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index d79d221..4e98ffa 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -156,15 +156,8 @@ static void poll_napi(struct net_device *dev)
 {
 	struct napi_struct *napi;
 	int budget = 16;
-	struct softnet_data *sd = &__get_cpu_var(softnet_data);
-	struct list_head *nlist;
 
-	if (dev->flags & IFF_MASTER)
-		nlist = &sd->poll_list;
-	else
-		nlist = &dev->napi_list;
-
-	list_for_each_entry(napi, nlist, dev_list) {
+	list_for_each_entry(napi, &dev->napi_list, dev_list) {
 		if (napi->poll_owner != smp_processor_id() &&
 		    spin_trylock(&napi->poll_lock)) {
 			budget = poll_one_napi(dev->npinfo, napi, budget);
-- 
1.7.2.3

Re: [PATCH] bonding: minor cleanups to bond + netpoll

[Andy Gospodarek]

On Tue, Oct 19, 2010 at 01:04:24PM -0400, nhorman@tuxdriver.com wrote:
> Testing that was onging when the the reset patchset to enable netpoll over
> bonding revealed some minor corner cases that are worth correcting.  In summary:
> 
> 1) Remove netpoll tx blocking from bond_release_all.  Its not needed and causes
> some uglyness when removing the bonding module, in the form of a backtrace that
> gets logged.  blocking isn't needed in this path anyway as the netconsole is
> already unregistered from us at this point
> 
> 2) Remove my changes to napi_poll.  Closer inspection of the bonding
> poll_controller show that we wind up recursively calling the napi poll routines
> for the slaves through sucsessive calls to netpoll_poll_dev.  My origional
> change is harmless, but its not really needed, so lets make the code simpler.
> 
> Further details available in the individual commit messages
> 
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> 

I've done some quick testing with these and they address the concerns I
raised with Neil about his first patch-set.

Signed-off-by: Andy Gospodarek <andy@greyhouse.net>

Re: [PATCH 1/2] Remove netpoll blocking from uninit path

[Cong Wang]

On 10/20/10 01:04, nhorman@tuxdriver.com wrote:
> From: Neil Horman<nhorman@tuxdriver.com>
>
> Some recent testing in netpoll with bonding showed this backtrace
>
>   ------------[ cut here ]------------
>   kernel BUG at drivers/net/bonding/bonding.h:134!
>   invalid opcode: 0000 [#1] SMP
>   last sysfs file: /sys/devices/pci0000:00/0000:00:1d.2/usb7/devnum
>   CPU 0
>   Pid: 1876, comm: rmmod Not tainted 2.6.36-rc3+ #10 D26928/
>   RIP: 0010:[<ffffffffa0514ba4>]  [<ffffffffa0514ba4>] bond_uninit+0x6f4/0x7a0
>   RSP: 0018:ffff88003b1b5d58  EFLAGS: 00010296
>   RAX: ffff88003b9b6200 RBX: ffff8800373e8e00 RCX: 00000000000f4240
>   RDX: 00000000ffffffff RSI: 0000000000000286 RDI: 0000000000000286
>   RBP: ffff88003b1b5dc8 R08: 0000000000000000 R09: 00000001af7de920
>   R10: 0000000000000000 R11: ffff880002495e98 R12: ffff880037922700
>   R13: ffff880038c31000 R14: ffff880037922730 R15: 0000000000000286
>   FS:  00007f90e6d72700(0000) GS:ffff880002400000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>   CR2: 000000346f0d9ad0 CR3: 000000003b263000 CR4: 00000000000006f0
>   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>   Process rmmod (pid: 1876, threadinfo ffff88003b1b4000, task ffff88003b36aa80)
>   Stack:
>   00000000ffffffff ffff88003b1b5d7a ffff8800379221e8 ffff880037922000
>   <0>  ffff88003b1b5dc8 ffffffff813eb5fb ffff88003b1b5da8 0000000031b177a3
>   <0>  ffff88003b1b5da8 ffff880037922000 ffff88003b1b5e48 ffff88003b1b5e48
>   Call Trace:
>   [<ffffffff813eb5fb>] ? rtmsg_ifinfo+0xcb/0xf0
>   [<ffffffff813daad8>] rollback_registered_many+0x168/0x280
>   [<ffffffff813dac09>] unregister_netdevice_many+0x19/0x80
>   [<ffffffff813e97b3>] __rtnl_kill_links+0x63/0x90
>   [<ffffffff813e980b>] __rtnl_link_unregister+0x2b/0x60
>   [<ffffffff813e9bde>] rtnl_link_unregister+0x1e/0x30
>   [<ffffffffa052124b>] bonding_exit+0x37/0x51 [bonding]
>   [<ffffffff81098b2e>] sys_delete_module+0x19e/0x270
>   [<ffffffff810bb2b2>] ? audit_syscall_entry+0x252/0x280
>   [<ffffffff8100b0b2>] system_call_fastpath+0x16/0x1b
>   RIP  [<ffffffffa0514ba4>] bond_uninit+0x6f4/0x7a0 [bonding]
>   RSP<ffff88003b1b5d58>
>   ---[ end trace 1395ad691cea24d1 ]---
>
> It occurs because of my recent netpoll blocking patches, which I added to avoid
> recursive deadlock in the bonding driver.  It relies on some per cpu bits, but
> the shutdown path forces some rescheduling as we cancel workqueues for the
> driver and wait for some device refcounts.  If after the forced reschedule, we
> wind up on a different cpu we trigger the bughalt in unblock_netpoll_tx.
>
> The fix is to remove the netpoll block/unblock calls from bond_release_all.
> This is safe to do because bond_uninit, which is called via ndo_uninit in
> rollback_registered_many, doesn't occur until we send a NETDEV_UNREGISTER event,
> which triggers netconsole to remove us as a netpoll client, so we are guaranteed
> not to recurse into our own tx path here.

Also bond_release_all() is called after bond_netpoll_cleanup()
in bond_uninit().

>
> Signed-off-by: Neil Horman<nhorman@tuxdriver.com>

Reviewed-by: WANG Cong <amwang@redhat.com>

Thanks.

Re: [PATCH 2/2] Revert napi_poll fix for bonding driver

[Cong Wang]

On 10/20/10 01:04, nhorman@tuxdriver.com wrote:
> From: Neil Horman<nhorman@tuxdriver.com>
>
> In an erlier patch I modified napi_poll so that devices with IFF_MASTER polled
> the per_cpu list instead of the device list for napi.  I did this because the
> bonding driver has no napi instances to poll, it instead expects to check the
> slave devices napi instances, which napi_poll was unaware of.  Looking at this
> more closely however, I now see this isn't strictly needed.  As the bond driver
> poll_controller calls the slaves poll_controller via netpoll_poll_dev, which
> recursively calls poll_napi on each slave, allowing those napi instances to get
> serviced.  The earlier patch isn't at all harmfull, its just not needed, so lets
> revert it to make the code cleaner.  Sorry for the noise,
>
> Signed-off-by: Neil Horman<nhorman@tuxdriver.com>

Looks reasonable to me,

Reviewed-by: WANG Cong <amwang@redhat.com>

Thanks.

Re: [PATCH 1/2] Remove netpoll blocking from uninit path

[David Miller]

From: Cong Wang <amwang@redhat.com>
Date: Wed, 20 Oct 2010 15:47:11 +0800

> On 10/20/10 01:04, nhorman@tuxdriver.com wrote:
>> From: Neil Horman<nhorman@tuxdriver.com>
>>
>> Some recent testing in netpoll with bonding showed this backtrace
...
>> Signed-off-by: Neil Horman<nhorman@tuxdriver.com>
> 
> Reviewed-by: WANG Cong <amwang@redhat.com>

Applied.

Neil, please add proper subsystem prefixes to your subject
lines, I've had to add them by hand as I add your patches.

Thanks.

Re: [PATCH 2/2] Revert napi_poll fix for bonding driver

[David Miller]

From: Cong Wang <amwang@redhat.com>
Date: Wed, 20 Oct 2010 15:52:00 +0800

> On 10/20/10 01:04, nhorman@tuxdriver.com wrote:
>> Signed-off-by: Neil Horman<nhorman@tuxdriver.com>
 ...
> Reviewed-by: WANG Cong <amwang@redhat.com>

Also applied, thanks.

Re: [PATCH 1/2] Remove netpoll blocking from uninit path

[Neil Horman]

On Wed, Oct 20, 2010 at 01:45:38AM -0700, David Miller wrote:
> From: Cong Wang <amwang@redhat.com>
> Date: Wed, 20 Oct 2010 15:47:11 +0800
> 
> > On 10/20/10 01:04, nhorman@tuxdriver.com wrote:
> >> From: Neil Horman<nhorman@tuxdriver.com>
> >>
> >> Some recent testing in netpoll with bonding showed this backtrace
> ...
> >> Signed-off-by: Neil Horman<nhorman@tuxdriver.com>
> > 
> > Reviewed-by: WANG Cong <amwang@redhat.com>
> 
> Applied.
> 
> Neil, please add proper subsystem prefixes to your subject
> lines, I've had to add them by hand as I add your patches.
> 
Copy that, apologies.

Thanks!
Neil

> Thanks.
>