linux-kernel - Re: [PATCH 10/15] ftrace: trace different functions with a different tracer

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Date:	Tue, 17 Feb 2009 13:53:58 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 10/15] ftrace: trace different functions with a different
 tracer


On Tue, 17 Feb 2009, Paul E. McKenney wrote:
> > This will unregister all functions matching glob that has an entry
> > pointing to ops.
> > 
> >   void unregister_ftrace_function_hook_all(char *glob)
> > 
> > This simply unregisters all funcs.
> 
> Looks like a nice addition!
> 
> One RCU type mismatch called out below.
> 
> > Signed-off-by: Steven Rostedt <srostedt@...hat.com>
> > ---
> >  include/linux/ftrace.h |   18 ++++
> >  kernel/trace/ftrace.c  |  247 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 265 insertions(+), 0 deletions(-)
> > 
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index f0a0ecc..13918c4 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -106,6 +106,24 @@ struct ftrace_func_command {
> >  /* asm/ftrace.h must be defined for archs supporting dynamic ftrace */
> >  #include <asm/ftrace.h>
> 
> [ . . . ]
> 
> > +
> > +static void
> > +__unregister_ftrace_function_hook(char *glob, struct ftrace_hook_ops *ops,
> > +				  void *data, int flags)
> > +{
> > +	struct ftrace_func_hook *entry;
> > +	struct hlist_node *n, *tmp;
> > +	char str[KSYM_SYMBOL_LEN];
> > +	int type = MATCH_FULL;
> > +	int i, len = 0;
> > +	char *search;
> > +
> > +	if (glob && (strcmp(glob, "*") || !strlen(glob)))
> > +		glob = NULL;
> > +	else {
> > +		int not;
> > +
> > +		type = ftrace_setup_glob(glob, strlen(glob), &search, &not);
> > +		len = strlen(search);
> > +
> > +		/* we do not support '!' for function hooks */
> > +		if (WARN_ON(not))
> > +			return;
> > +	}
> > +
> > +	mutex_lock(&ftrace_lock);
> > +	for (i = 0; i < FTRACE_FUNC_HASHSIZE; i++) {
> > +		struct hlist_head *hhd = &ftrace_func_hash[i];
> > +
> > +		hlist_for_each_entry_safe(entry, n, tmp, hhd, node) {
> > +
> > +			/* break up if statements for readability */
> > +			if ((flags & HOOK_TEST_FUNC) && entry->ops != ops)
> > +				continue;
> > +
> > +			if ((flags & HOOK_TEST_DATA) && entry->data != data)
> > +				continue;
> > +
> > +			/* do this last, since it is the most expensive */
> > +			if (glob) {
> > +				kallsyms_lookup(entry->ip, NULL, NULL,
> > +						NULL, str);
> > +				if (!ftrace_match(str, glob, len, type))
> > +					continue;
> > +			}
> > +
> > +			hlist_del(&entry->node);
> > +			call_rcu(&entry->rcu, ftrace_free_entry_rcu);
> 
> This should be call_rcu_sched() to match the preemption disabling.

Thanks! I should have CC'd you on that. I thought that was not right.
Will fix.

-- Steve

> 
> > +		}
> > +	}
> > +	__disable_ftrace_function_hook();
> > +	mutex_unlock(&ftrace_lock);
> > +}
> 
> 
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