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Date: Wed, 8 Jan 2014 05:28:52 -0800 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Oleg Nesterov <oleg@...hat.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Al Viro <viro@...IV.linux.org.uk>, Dipankar Sarma <dipankar@...ibm.com>, Eric Dumazet <edumazet@...gle.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 0/2] rcu_dereference_check_fdtable fix/cleanups On Tue, Jan 07, 2014 at 07:12:58PM +0100, Oleg Nesterov wrote: > Hello. > > I tried to audit the users of thread_group_empty() (we need > to change it) and found rcu_my_thread_group_empty() which > looks wrong. > > The patches look simple, but I am not sure it is fine to use > rcu_lock_acquire() directly. Perhaps it makes sense to add a > new helper? Note that we have more users which take rcu lock > only to shut up lockdep. Please review. > > And I am a bit confused. Perhaps rcu_lock_acquire() should > depend on CONFIG_PROVE_RCU, not on CONFIG_DEBUG_LOCK_ALLOC? > We only need rcu_lock_map/etc for rcu_lockdep_assert(). I am not all that excited about invoking rcu_lock_acquire() outside of RCU... Another approach would be to add an argument to files_fdtable() that is zero normally and one for "we know we don't need RCU protection." Then rcu_dereference_check() could be something like the following: #define files_fdtable(files, c) \ (rcu_dereference_check_fdtable((files), (files)->fdt) || c) Would that work? Thanx, Paul > Oleg. > > fs/file.c | 24 +++++++++++------------- > include/linux/fdtable.h | 19 +++++++++++++------ > include/linux/rcupdate.h | 2 -- > kernel/rcu/update.c | 11 ----------- > 4 files changed, 24 insertions(+), 32 deletions(-) > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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