14cd5d4a01
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.
However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.
It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't handle comments, leaving references
to ACCESS_ONCE() instances which have been removed. As a preparatory
step, this patch converts netlink and netfilter code and comments to use
{READ,WRITE}_ONCE() consistently.
----
virtual patch
@ depends on patch @
expression E1, E2;
@@
- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)
@ depends on patch @
expression E;
@@
- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Florian Westphal <fw@strlen.de>
Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-7-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
43 lines
1.4 KiB
C
43 lines
1.4 KiB
C
#ifndef __LINUX_GENERIC_NETLINK_H
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#define __LINUX_GENERIC_NETLINK_H
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#include <uapi/linux/genetlink.h>
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/* All generic netlink requests are serialized by a global lock. */
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extern void genl_lock(void);
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extern void genl_unlock(void);
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#ifdef CONFIG_LOCKDEP
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extern bool lockdep_genl_is_held(void);
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#endif
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/* for synchronisation between af_netlink and genetlink */
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extern atomic_t genl_sk_destructing_cnt;
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extern wait_queue_head_t genl_sk_destructing_waitq;
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/**
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* rcu_dereference_genl - rcu_dereference with debug checking
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* @p: The pointer to read, prior to dereferencing
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*
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* Do an rcu_dereference(p), but check caller either holds rcu_read_lock()
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* or genl mutex. Note : Please prefer genl_dereference() or rcu_dereference()
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*/
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#define rcu_dereference_genl(p) \
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rcu_dereference_check(p, lockdep_genl_is_held())
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/**
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* genl_dereference - fetch RCU pointer when updates are prevented by genl mutex
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* @p: The pointer to read, prior to dereferencing
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*
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* Return the value of the specified RCU-protected pointer, but omit
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* both the smp_read_barrier_depends() and the READ_ONCE(), because
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* caller holds genl mutex.
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*/
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#define genl_dereference(p) \
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rcu_dereference_protected(p, lockdep_genl_is_held())
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#define MODULE_ALIAS_GENL_FAMILY(family)\
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MODULE_ALIAS_NET_PF_PROTO_NAME(PF_NETLINK, NETLINK_GENERIC, "-family-" family)
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#endif /* __LINUX_GENERIC_NETLINK_H */
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