netdev - Re: [PATCH net v2] net: sched: don't use GFP

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Message-ID: <1504631869.15310.46.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 05 Sep 2017 10:17:49 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, jiri@...nulli.us,
        Chris Mi <chrism@...lanox.com>, xiyou.wangcong@...il.com,
        jhs@...atatu.com, oss-drivers@...ronome.com
Subject: Re: [PATCH net v2] net: sched: don't use GFP_KERNEL under spin lock

On Tue, 2017-09-05 at 08:31 -0700, Jakub Kicinski wrote:
> The new TC IDR code uses GFP_KERNEL under spin lock.  Which leads
> to:
> 
> [  582.621091] BUG: sleeping function called from invalid context at ../mm/slab.h:416
> [  582.629721] in_atomic(): 1, irqs_disabled(): 0, pid: 3379, name: tc
> [  582.636939] 2 locks held by tc/3379:
> [  582.641049]  #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff910354ce>] rtnetlink_rcv_msg+0x92e/0x1400
> [  582.650958]  #1:  (&(&tn->idrinfo->lock)->rlock){+.-.+.}, at: [<ffffffff9110a5e0>] tcf_idr_create+0x2f0/0x8e0
> [  582.662217] Preemption disabled at:
> [  582.662222] [<ffffffff9110a5e0>] tcf_idr_create+0x2f0/0x8e0
> [  582.672592] CPU: 9 PID: 3379 Comm: tc Tainted: G        W       4.13.0-rc7-debug-00648-g43503a79b9f0 #287
> [  582.683432] Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.3.4 11/08/2016
> [  582.691937] Call Trace:
> ...
> [  582.742460]  kmem_cache_alloc+0x286/0x540
> [  582.747055]  radix_tree_node_alloc.constprop.6+0x4a/0x450
> [  582.753209]  idr_get_free_cmn+0x627/0xf80
> ...
> [  582.815525]  idr_alloc_cmn+0x1a8/0x270
> ...
> [  582.833804]  tcf_idr_create+0x31b/0x8e0
> ...
> 
> Try to preallocate the memory with idr_prealloc(GFP_KERNEL)
> (as suggested by Eric Dumazet), and change the allocation 
> flags under spin lock.
> 
> Fixes: 65a206c01e8e ("net/sched: Change act_api and act_xxx modules to use IDR")
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Reviewed-by: Simon Horman <simon.horman@...ronome.com>
> ---


Acked-by: Eric Dumazet <edumazet@...gle.com>

Not related to your patch, but it looks like idr_preload() has a bug
added in 4.11.  I will send a fix to lkml.