Messages in this thread | | | Subject | Re: [PATCH v2] perf/core: fix RCU issues with cgroup monitoring mode | From | Eric Dumazet <> | Date | Tue, 27 Oct 2015 13:24:05 -0700 |
| |
On Tue, 2015-10-27 at 20:25 +0100, Stephane Eranian wrote: > This patch eliminates all known RCU violations detected > by the RCU checker (PROVE_RCU). The impact code paths > were all related to cgroup mode monitoring and involved > access a task's cgrp. > > V2 is updated to include suggestions from PeterZ to eliminate > some of the warnings without grabbing the rcu_read lock because > we know we are already holding the ctx->lock which prevents > the cgroup from disappearing while we are accessing it. > The trick, as suggested by Peter, is to modify the > perf_cgroup_from_task() to take an extra boolean parameter > to allow bypassing the lockdep test in the task_subsys_cstate() > macros. This patch uses this approach to update all calls the > perf_cgroup_from_task(). > V2 Patch relative to: > 8b3c8e6 Revert "rculist: Make list_entry_rcu() use lockless_dereference()" > > Signed-off-by: Stephane Eranian <eranian@google.com> > ---
Instead trusting caller to provide correct 'safe' boolean, what about using lockdep_is_held() ?
This way, you keep full lockep support.
A random example is
#define rcu_dereference_rtnl(p) rcu_dereference_check(p, lockdep_rtnl_is_held())
| |