Messages in this thread | | | Date | Sat, 1 Oct 2005 11:00:28 -0700 (PDT) | From | Suzanne Wood <> | Subject | Re: [RFC][PATCH] identify in_dev_get rcu read-side critical sections |
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With the spotlight leaving in_dev_get, we have the parallel question of in_dev_put() and __in_dev_put() both defined with refcnt decrement, but the preceding underscore may lend itself to an inadvertant pairing and refcnt inaccuracy.
In the following cscope of linux-2.6.14-rc2 prior to Herbert's patches which remove the occurence in pktgen.c and the others are paired with __in_dev_get_rtnl(), except xfrm4_policy.c():
C symbol: __in_dev_put File Function Line File Function Line 0 inetdevice.h <global> 172 #define __in_dev_put(idev) atomic_dec(&(idev)->refcnt) 1 pktgen.c pktgen_setup_inject 1687 __in_dev_put(in_dev); 2 devinet.c inet_rtm_deladdr 412 __in_dev_put(in_dev); 3 igmp.c igmp_gq_timer_expire 686 __in_dev_put(in_dev); 4 igmp.c igmp_ifc_timer_expire 698 __in_dev_put(in_dev); 5 igmp.c igmp_heard_query 801 __in_dev_put(in_dev); 6 igmp.c ip_mc_down 1228 __in_dev_put(in_dev); 7 igmp.c ip_mc_down 1231 __in_dev_put(in_dev); 8 igmp.c ip_mc_find_dev 1310 __in_dev_put(idev); 9 xfrm4_policy.c xfrm4_dst_ifdown 280 __in_dev_put(loopback_idev);
It may not be reasonable to rename __in_dev_put for its parallel definition since its current usage is with __in_dev_get_rtnl() which does not increment refcnt.
It is also probably good to retain the old __in_dev_get() and __in_dev_put() and deprecate them.
Old business: this is probably stating the obvious, with Herbert's patches in place, none of the test patch I'd submitted 8 Sept should take effect.
Thank you. Suzanne
----- Original Message ----- From: "Herbert Xu" <herbert@gondor.apana.org.au> Sent: Saturday, October 01, 2005 12:12 AM
> On Fri, Sep 30, 2005 at 11:56:41PM -0700, Suzanne Wood wrote: >> >> The other thing I'd hoped to address in pktgen.c was >> removing the __in_dev_put() which decrements refcnt >> while __in_dev_get_rcu() does not increment. > > Well spotted. > > Here is a patch on top of the last one to fix this bogus decrement. > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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