Re: FAILED: patch "[PATCH] powerpc/pseries: Fix unitialized timer reset on migration" failed to apply to 4.4-stable tree

[Michael Bringmann <mwb@linux.vnet.ibm.com>]

To backport the patc

    commit 8604895a34d92f5e186ceb931b0d1b384030ea3d

to the 4.4-stable tree, please try the following backport:

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
--- a/arch/powerpc/mm/numa.c	2018-10-02 09:03:06.232491410 -0500
+++ b/arch/powerpc/mm/numa.c	2018-10-02 09:04:17.152494472 -0500
@@ -1606,7 +1606,8 @@
 {
 	topology_timer.data = 0;
 	topology_timer.expires = jiffies + topology_timer_secs * HZ;
-	mod_timer(&topology_timer, topology_timer.expires);
+	if (vphn_enabled)
+		mod_timer(&topology_timer, topology_timer.expires);
 }
 
 #ifdef CONFIG_SMP



On 10/02/2018 07:18 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 
>>>From 8604895a34d92f5e186ceb931b0d1b384030ea3d Mon Sep 17 00:00:00 2001
> From: Michael Bringmann <mwb@linux.vnet.ibm.com>
> Date: Thu, 20 Sep 2018 11:45:13 -0500
> Subject: [PATCH] powerpc/pseries: Fix unitialized timer reset on migration
> 
> After migration of a powerpc LPAR, the kernel executes code to
> update the system state to reflect new platform characteristics.
> 
> Such changes include modifications to device tree properties provided
> to the system by PHYP. Property notifications received by the
> post_mobility_fixup() code are passed along to the kernel in general
> through a call to of_update_property() which in turn passes such
> events back to all modules through entries like the '.notifier_call'
> function within the NUMA module.
> 
> When the NUMA module updates its state, it resets its event timer. If
> this occurs after a previous call to stop_topology_update() or on a
> system without VPHN enabled, the code runs into an unitialized timer
> structure and crashes. This patch adds a safety check along this path
> toward the problem code.
> 
> An example crash log is as follows.
> 
>   ibmvscsi 30000081: Re-enabling adapter!
>   ------------[ cut here ]------------
>   kernel BUG at kernel/time/timer.c:958!
>   Oops: Exception in kernel mode, sig: 5 [#1]
>   LE SMP NR_CPUS=2048 NUMA pSeries
>   Modules linked in: nfsv3 nfs_acl nfs tcp_diag udp_diag inet_diag lockd unix_diag af_packet_diag netlink_diag grace fscache sunrpc xts vmx_crypto pseries_rng sg binfmt_misc ip_tables xfs libcrc32c sd_mod ibmvscsi ibmveth scsi_transport_srp dm_mirror dm_region_hash dm_log dm_mod
>   CPU: 11 PID: 3067 Comm: drmgr Not tainted 4.17.0+ #179
>   ...
>   NIP mod_timer+0x4c/0x400
>   LR  reset_topology_timer+0x40/0x60
>   Call Trace:
>     0xc0000003f9407830 (unreliable)
>     reset_topology_timer+0x40/0x60
>     dt_update_callback+0x100/0x120
>     notifier_call_chain+0x90/0x100
>     __blocking_notifier_call_chain+0x60/0x90
>     of_property_notify+0x90/0xd0
>     of_update_property+0x104/0x150
>     update_dt_property+0xdc/0x1f0
>     pseries_devicetree_update+0x2d0/0x510
>     post_mobility_fixup+0x7c/0xf0
>     migration_store+0xa4/0xc0
>     kobj_attr_store+0x30/0x60
>     sysfs_kf_write+0x64/0xa0
>     kernfs_fop_write+0x16c/0x240
>     __vfs_write+0x40/0x200
>     vfs_write+0xc8/0x240
>     ksys_write+0x5c/0x100
>     system_call+0x58/0x6c
> 
> Fixes: 5d88aa85c00b ("powerpc/pseries: Update CPU maps when device tree is updated")
> Cc: stable@vger.kernel.org # v3.10+
> Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> 
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index 35ac5422903a..b5a71baedbc2 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -1452,7 +1452,8 @@ static struct timer_list topology_timer;
> 
>  static void reset_topology_timer(void)
>  {
> -	mod_timer(&topology_timer, jiffies + topology_timer_secs * HZ);
> +	if (vphn_enabled)
> +		mod_timer(&topology_timer, jiffies + topology_timer_secs * HZ);
>  }
> 
>  #ifdef CONFIG_SMP
> 
> 

-- 
Michael W. Bringmann
Linux Technology Center
IBM Corporation
Tie-Line  363-5196
External: (512) 286-5196
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mwb@linux.vnet.ibm.com