Messages in this thread | | | Date | Thu, 23 Sep 2010 10:23:37 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 5/8] rcu: only one evaluation of arg in rcu_dereference_check() unless sparse |
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On Thu, Sep 23, 2010 at 03:13:39PM +0200, Arnd Bergmann wrote: > On Thursday 23 September 2010, Paul E. McKenney wrote: > > The current version of the __rcu_access_pointer(), __rcu_dereference_check(), > > and __rcu_dereference_protected() macros evaluate their "p" argument > > three times, not counting typeof()s. This is bad news if that argument > > contains a side effect. This commit therefore evaluates this argument > > only once in normal kernel builds. However, the straightforward approach > > defeats sparse's RCU-pointer checking, so when __CHECKER__ is defined, > > the additional pair of evaluations of the "p" argument are performed in > > order to permit sparse to detect misuse of RCU-protected pointers. > > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Sorry for not following up with the alternative approach yet. We can always > do that later, for your patch should go into 2.6.36 to fix any problems > arising from unintended macro side-effects. > > Acked-by: Arnd Bergmann <arnd@arndb.de>
No problem, when you get me a better approach, I will happily queue it!
Thanx, Paul
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