Messages in this thread Patch in this message | | | Date | Fri, 28 Jun 2013 16:27:44 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH] tracing/kprobe: Recover old array if fails to enable kprobe |
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On 06/28, Masami Hiramatsu wrote: > > @@ -232,19 +246,21 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) > rcu_assign_pointer(tp->files, new); > tp->flags |= TP_FLAG_TRACE; > > + ret = __enable_trace_probe(tp); > + if (ret < 0) { > + /* Write back the old list */ > + rcu_assign_pointer(tp->files, old); > + old = new; /* "new" must be freed */ > + } > + > if (old) { > /* Make sure the probe is done with old files */ > synchronize_sched(); > kfree(old); > }
Ah, but this conflicts with the other changes I sent. They have your acks, and iiuc Steven is going to apply them.
Besides, this fix is not complete afaics, we should also clear TP_FLAG_TRACE/PROFILE if __enable_trace_probe() fails.
Perhaps you can do this later, on top of the pending changes?
Or. Given that this patch assumes that enable_kprobe() must succed, can't we make a minimal change for now?
------------------------------------------------------------------------------- [PATCH] tracing/kprobe: WARN() if enable_kprobe() fails.
enable_trace_probe() doesn't recover tp->files/flags if enable_kprobe() fails, this looks confusing.
However, enable_kprobe() must not fail at this time except for unknown bug or changing the implementation of enable_kprobe(), because usual failure cases (not registered or gone) are already filtered.
So this patch simply adds WARN_ON(ret) to document this fact, even if it makes sense to cleanup the logic anyway later.
Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/trace/trace_kprobe.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 5c070db..bb608b5 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -220,6 +220,7 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) ret = enable_kretprobe(&tp->rp); else ret = enable_kprobe(&tp->rp.kp); + WARN_ON(ret); } out: return ret;
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