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In case the qdisc_match_from_root function() is called from non-rcu path
with rtnl mutex held, a suspiciout rcu usage warning appears:

[  241.504354] =============================
[  241.504358] WARNING: suspicious RCU usage
[  241.504366] 5.8.0-rc4-custom-01521-g72a7c7d549c3 #32 Not tainted
[  241.504370] -----------------------------
[  241.504378] net/sched/sch_api.c:270 RCU-list traversed in non-reader section!!
[  241.504382]
               other info that might help us debug this:
[  241.504388]
               rcu_scheduler_active = 2, debug_locks = 1
[  241.504394] 1 lock held by tc/1391:
[  241.504398]  #0: ffffffff85a27850 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x49a/0xbd0
[  241.504431]
               stack backtrace:
[  241.504440] CPU: 0 PID: 1391 Comm: tc Not tainted 5.8.0-rc4-custom-01521-g72a7c7d549c3 #32
[  241.504446] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-2.fc32 04/01/2014
[  241.504453] Call Trace:
[  241.504465]  dump_stack+0x100/0x184
[  241.504482]  lockdep_rcu_suspicious+0x153/0x15d
[  241.504499]  qdisc_match_from_root+0x293/0x350

Fix this by passing the rtnl held lockdep condition down to
hlist_for_each_entry_rcu()

Reported-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
4 contributors

Users who have contributed to this file

@sashalevin @jpirko @gregkh @aik
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Statically sized hash table implementation
* (C) 2012 Sasha Levin <levinsasha928@gmail.com>
*/
#ifndef _LINUX_HASHTABLE_H
#define _LINUX_HASHTABLE_H
#include <linux/list.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/hash.h>
#include <linux/rculist.h>
#define DEFINE_HASHTABLE(name, bits) \
struct hlist_head name[1 << (bits)] = \
{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
#define DEFINE_READ_MOSTLY_HASHTABLE(name, bits) \
struct hlist_head name[1 << (bits)] __read_mostly = \
{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
#define DECLARE_HASHTABLE(name, bits) \
struct hlist_head name[1 << (bits)]
#define HASH_SIZE(name) (ARRAY_SIZE(name))
#define HASH_BITS(name) ilog2(HASH_SIZE(name))
/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
#define hash_min(val, bits) \
(sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits))
static inline void __hash_init(struct hlist_head *ht, unsigned int sz)
{
unsigned int i;
for (i = 0; i < sz; i++)
INIT_HLIST_HEAD(&ht[i]);
}
/**
* hash_init - initialize a hash table
* @hashtable: hashtable to be initialized
*
* Calculates the size of the hashtable from the given parameter, otherwise
* same as hash_init_size.
*
* This has to be a macro since HASH_BITS() will not work on pointers since
* it calculates the size during preprocessing.
*/
#define hash_init(hashtable) __hash_init(hashtable, HASH_SIZE(hashtable))
/**
* hash_add - add an object to a hashtable
* @hashtable: hashtable to add to
* @node: the &struct hlist_node of the object to be added
* @key: the key of the object to be added
*/
#define hash_add(hashtable, node, key) \
hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
/**
* hash_add_rcu - add an object to a rcu enabled hashtable
* @hashtable: hashtable to add to
* @node: the &struct hlist_node of the object to be added
* @key: the key of the object to be added
*/
#define hash_add_rcu(hashtable, node, key) \
hlist_add_head_rcu(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
/**
* hash_hashed - check whether an object is in any hashtable
* @node: the &struct hlist_node of the object to be checked
*/
static inline bool hash_hashed(struct hlist_node *node)
{
return !hlist_unhashed(node);
}
static inline bool __hash_empty(struct hlist_head *ht, unsigned int sz)
{
unsigned int i;
for (i = 0; i < sz; i++)
if (!hlist_empty(&ht[i]))
return false;
return true;
}
/**
* hash_empty - check whether a hashtable is empty
* @hashtable: hashtable to check
*
* This has to be a macro since HASH_BITS() will not work on pointers since
* it calculates the size during preprocessing.
*/
#define hash_empty(hashtable) __hash_empty(hashtable, HASH_SIZE(hashtable))
/**
* hash_del - remove an object from a hashtable
* @node: &struct hlist_node of the object to remove
*/
static inline void hash_del(struct hlist_node *node)
{
hlist_del_init(node);
}
/**
* hash_del_rcu - remove an object from a rcu enabled hashtable
* @node: &struct hlist_node of the object to remove
*/
static inline void hash_del_rcu(struct hlist_node *node)
{
hlist_del_init_rcu(node);
}
/**
* hash_for_each - iterate over a hashtable
* @name: hashtable to iterate
* @bkt: integer to use as bucket loop cursor
* @obj: the type * to use as a loop cursor for each entry
* @member: the name of the hlist_node within the struct
*/
#define hash_for_each(name, bkt, obj, member) \
for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
(bkt)++)\
hlist_for_each_entry(obj, &name[bkt], member)
/**
* hash_for_each_rcu - iterate over a rcu enabled hashtable
* @name: hashtable to iterate
* @bkt: integer to use as bucket loop cursor
* @obj: the type * to use as a loop cursor for each entry
* @member: the name of the hlist_node within the struct
*/
#define hash_for_each_rcu(name, bkt, obj, member) \
for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
(bkt)++)\
hlist_for_each_entry_rcu(obj, &name[bkt], member)
/**
* hash_for_each_safe - iterate over a hashtable safe against removal of
* hash entry
* @name: hashtable to iterate
* @bkt: integer to use as bucket loop cursor
* @tmp: a &struct hlist_node used for temporary storage
* @obj: the type * to use as a loop cursor for each entry
* @member: the name of the hlist_node within the struct
*/
#define hash_for_each_safe(name, bkt, tmp, obj, member) \
for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
(bkt)++)\
hlist_for_each_entry_safe(obj, tmp, &name[bkt], member)
/**
* hash_for_each_possible - iterate over all possible objects hashing to the
* same bucket
* @name: hashtable to iterate
* @obj: the type * to use as a loop cursor for each entry
* @member: the name of the hlist_node within the struct
* @key: the key of the objects to iterate over
*/
#define hash_for_each_possible(name, obj, member, key) \
hlist_for_each_entry(obj, &name[hash_min(key, HASH_BITS(name))], member)
/**
* hash_for_each_possible_rcu - iterate over all possible objects hashing to the
* same bucket in an rcu enabled hashtable
* @name: hashtable to iterate
* @obj: the type * to use as a loop cursor for each entry
* @member: the name of the hlist_node within the struct
* @key: the key of the objects to iterate over
*/
#define hash_for_each_possible_rcu(name, obj, member, key, cond...) \
hlist_for_each_entry_rcu(obj, &name[hash_min(key, HASH_BITS(name))],\
member, ## cond)
/**
* hash_for_each_possible_rcu_notrace - iterate over all possible objects hashing
* to the same bucket in an rcu enabled hashtable in a rcu enabled hashtable
* @name: hashtable to iterate
* @obj: the type * to use as a loop cursor for each entry
* @member: the name of the hlist_node within the struct
* @key: the key of the objects to iterate over
*
* This is the same as hash_for_each_possible_rcu() except that it does
* not do any RCU debugging or tracing.
*/
#define hash_for_each_possible_rcu_notrace(name, obj, member, key) \
hlist_for_each_entry_rcu_notrace(obj, \
&name[hash_min(key, HASH_BITS(name))], member)
/**
* hash_for_each_possible_safe - iterate over all possible objects hashing to the
* same bucket safe against removals
* @name: hashtable to iterate
* @obj: the type * to use as a loop cursor for each entry
* @tmp: a &struct hlist_node used for temporary storage
* @member: the name of the hlist_node within the struct
* @key: the key of the objects to iterate over
*/
#define hash_for_each_possible_safe(name, obj, tmp, member, key) \
hlist_for_each_entry_safe(obj, tmp,\
&name[hash_min(key, HASH_BITS(name))], member)
#endif