Messages in this thread | | | Date | Mon, 19 Mar 2012 21:16:34 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Suspend-to-ram not working when ftrace is enabled, again! |
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Hi,
If tracing is enabled and we are tracing low-level suspend-to-ram related functions like restore_processor_state() etc (which are included by default in the list of traced functions), and we try suspending the machine, the machine doesn't resume. It reboots instead. (If we trace some unrelated functions like kzalloc() for example, there is no problem with suspend/resume).
Looking at https://lkml.org/lkml/2008/8/27/177, it appears that this is an old problem and also had a workaround (disabling tracing around suspend). The above patch corresponds to commit id: f42ac38c59 (ftrace: disable tracing for suspend to ram), which went in around 2.6.27 I think. But then commit cbe2f5a6e84 (tracing: allow tracing of suspend/resume & hibernation code again) reverted that commit.
And from https://lkml.org/lkml/2008/8/21/349, it looks like 2.6.28 and further was supposed to be problem-free. But unfortunately this problem has resurfaced.
I tested kernel 2.6.32.54 and I observed that the machine reboots during resume, which looks exactly like the problem discussed in the link above.
In another machine, I tested 3.3-rc6 and it doesn't seem to respond to resume events (like button press, lid open) at all. It just seems to remain suspended forever.
Should we resort to disabling ftrace around suspend again? Or do we have a better solution this time around?
Regards, Srivatsa S. Bhat
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