andy git 06/15 suspend/resume observations

Andy Green andy at
Fri Jun 20 09:17:46 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| Andy Green wrote:
|> Hash: SHA1
|> Somebody in the thread at some point said:
|> | Some deadlock would fit well, something spinning for some reason, I
|> | wonder what happens if we blow a NULL pointer exception at that time, a
|> | full panic or the kind of "I just killed that driver" thing that
|> | in normal Linux?
|> Oooh interesting, if I force a NULL exception
|>     int *p = NULL;
|> ...
|>     printk(KERN_ERR "die on a null %d\n", *p);
|> in the neo1973-pm-gsm resume function, I get the behaviour Sean reports,
|> does not complete resume, usb0 responds to pings, did not panic.
| There's not a whole lot to cause an NPD exception there, but it
| certainly offers a clue that something may be awry, if not in that
| driver at least in one nearby (in the temporal sense).

Agreed, about the time shifted damage aspect too.

| With the latest kernel, I get wonderful resumes -- almost all of the
| time.  But once in a while, usually when I've forgotten about the phone
| and I come back to it after 30 minutes or more, then it fails to resume.
|  Requires the battery to be pulled to come back...

I'm pretty certain the delay part of this is just increasing the
probability of GSM-side wake occurring, which is the true trigger.
That's why I was real happy with Sean's test that defeating GSM
operation made everything clean with suspend-resume, the monster lives
only in the GSM / serial side and not something WAAY more terrifying
like hardware instability over time.

I have a patch coming that if I can get it working will give a new way
to probe failed resume for evidence of the cause, and my guess is if it
works we will fix this as soon as we see what is in the currently hidden
syslog from resume on either of your devices showing symptoms.

- -Andy
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