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 17:17:11 -0700 |
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On Tue, 2015-10-27 at 16:37 -0700, Stephane Eranian wrote:
> But that macro is already embedded into the task_css_set() macro. > What we are saying here is that we have another way of ensuring the > cgroup cannot disappear here, and thus the rcu lockdep detects we > are not holding the rcu read lock but we know this is okay. We are > trying to avoid grabbing the rcu read lock when it is not really needed > to guarantee correct execution. So we are just shutting up the lockdep > in these particular cases by passing true as the safe argument value.
Sure, but in lockdep verbs, the following :
+ /* holding ctx->lock, so cgroup access is safe */ + cgrp = perf_cgroup_from_task(task, true);
would map to :
cgrp = perf_cgroup_from_task(task, lockdep_is_held(&ctx->lock));
Notice the comment becomes useless.
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