Messages in this thread | | | Date | Mon, 25 Jan 2010 21:58:16 +0100 | From | Frederic Weisbecker <> | Subject | Re: [RFC PATCH 03/10] ftrace: Drop the ftrace_profile_enabled checks in tracing hot path |
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On Fri, Jan 22, 2010 at 07:34:51AM -0500, Mathieu Desnoyers wrote: > * Steven Rostedt (rostedt@goodmis.org) wrote: > > On Thu, 2010-01-21 at 23:09 -0500, Mathieu Desnoyers wrote: > > > * Steven Rostedt (rostedt@goodmis.org) wrote: > > > > > > Hmm, interesting. Maybe something like that might work. But what if > > > > CONFIG_PREEMPT is enabled but CONFIG_FREEZER is not? > > > > > > Then you may want to make the function tracer depend on CONFIG_FREEZER, > > > but maybe Masami has other ideas ? > > > > egad no! This is just to help add guarantees to those that use the > > function tracer that when the tracing is disabled, it is guaranteed that > > no more tracing will be called by the function tracer. Currently, > > nothing relies on this. But we may add cases that might need this. > > Yep, identifying tracer quiescent state can become handy. > > > > > In fact, only those that need this requirement would need to do this > > trick. Anyway, we could make those depend on CONFIG_FREEZER, but that > > just seems to be a strange dependency. > > This makes me wonder (question for Masami)... > > static int __kprobes check_safety(void) > { > int ret = 0; > #if defined(CONFIG_PREEMPT) && defined(CONFIG_FREEZER) > ret = freeze_processes(); > if (ret == 0) { > struct task_struct *p, *q; > do_each_thread(p, q) { > if (p != current && p->state == TASK_RUNNING && > p->pid != 0) { > printk("Check failed: %s is running\n",p->comm); > ret = -1; > goto loop_end; > } > } while_each_thread(p, q);
How does that deal with kernel threads that don't freeze?
Also freezing every processes seems a bit of a heavy thing for that. Looks like a synchronize_tasks() would be really useful.
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