The big suspend mess

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To: Paul Mackerras <paulus@...>
Cc: Rafael J. Wysocki <rjw@...>, Benjamin Herrenschmidt <benh@...>, Matthew Garrett <mjg59@...>, <linux-kernel@...>, Pavel Machek <pavel@...>, <linux-pm@...>
Date: Wednesday, July 4, 2007 - 6:19 pm

On Wed, Jul 04, 2007 at 01:29:49PM +1000, Paul Mackerras wrote:

You forget one important point:
Regressions are much worse than normal bugs.

It's not about the question whether the driver was "correct" or
"buggy" - for a user the important question is whether it worked in 
practice, and if yes, whether it continues to work.

And my impression is that every time someone touches some part of the 
suspend code some drivers break.

During 2.6.21-rc, it wasn't unusual for users to run with one kernel 
into up to three distinct suspend regressions on one machine.

And no, it wasn't always the same set of distinct regressions.

IMHO the suspend code is currently way too much of a moving target which 
results in this mess.

The correct order seems to be:
1. agree on what the suspend code as a whole should look like
2. implement this
3. fix ALL drivers to work at least as good as they do today
4. get it tested in -mm
5. fix all bugs people run into
6. submit it for inclusion in Linus' tree
7. quickly work on the most likely big amount of bug reports

Step 1 is the most important one - evolving code is often something 
good, but in this case with different people trying to evolve the 
suspend code in different directions it simply results in a big mess.


cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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Messages in current thread:
[PATCH] Remove process freezer from suspend to RAM pathway, Matthew Garrett, (Tue Jul 3, 12:29 am)
Re: sysrq-t dumps of s2ram/fuse deadlock, Jeremy Maitin-Shepard, (Wed Jul 11, 9:45 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 1:48 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 3:19 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 5:14 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Thu Jul 5, 6:46 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Thu Jul 5, 7:20 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Thu Jul 5, 11:54 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Fri Jul 6, 12:41 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sat Jul 7, 12:06 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sat Jul 7, 8:48 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 1:14 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 5:20 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Mon Jul 9, 6:05 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Mon Jul 9, 5:13 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Mon Jul 9, 5:33 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 8:33 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 9:32 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 5:03 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 5:54 pm)
Re: hibernation/snapshot design, Jeremy Maitin-Shepard, (Mon Jul 9, 11:23 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 1:19 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Thu Jul 5, 11:59 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Fri Jul 6, 11:44 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sat Jul 7, 8:42 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 12:39 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sun Jul 8, 5:21 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Mon Jul 9, 5:14 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Sat Jul 7, 8:40 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Fri Jul 6, 5:03 am)
The big suspend mess, Adrian Bunk, (Wed Jul 4, 6:19 pm)
Re: [linux-pm] The big suspend mess, Alan Stern, (Thu Jul 5, 10:14 am)
Re: The big suspend mess, Pavel Machek, (Wed Jul 4, 8:27 pm)
Re: The big suspend mess, Adrian Bunk, (Wed Jul 4, 9:22 pm)
Re: The big suspend mess, Rafael J. Wysocki, (Thu Jul 5, 8:18 am)
Re: The big suspend mess, Paul Mackerras, (Wed Jul 4, 8:53 pm)
Re: The big suspend mess, Pavel Machek, (Thu Jul 5, 5:32 am)
Re: The big suspend mess, Gabriel C, (Thu Jul 5, 6:29 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Rafael J. Wysocki, (Wed Jul 4, 10:30 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 5:35 pm)
Re: removing refrigerator does not help with s2ram vs. fuse ..., Rafael J. Wysocki, (Thu Jul 5, 10:28 am)
Re: removing refrigerator does not help with s2ram vs. fuse ..., Rafael J. Wysocki, (Thu Jul 5, 10:41 am)
Re: removing refrigerator does not help with s2ram vs. fuse ..., Rafael J. Wysocki, (Thu Jul 5, 11:04 am)
Re: removing refrigerator does not help with s2ram vs. fuse ..., Rafael J. Wysocki, (Thu Jul 5, 11:27 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Thu Jul 5, 6:59 pm)
Re: malicious filesystems (was Re: [linux-pm] Re: [PATCH] Re..., Rafael J. Wysocki, (Sun Jul 8, 10:06 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Thu Jul 5, 7:05 pm)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Jeremy Maitin-Shepard, (Thu Jul 5, 11:59 pm)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Fri Jul 6, 4:59 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Fri Jul 6, 10:44 pm)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Sat Jul 7, 8:50 pm)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Fri Jul 6, 10:46 pm)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Rafael J. Wysocki, (Thu Jul 5, 10:14 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Thu Jul 5, 6:38 pm)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Rafael J. Wysocki, (Thu Jul 5, 10:02 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Rafael J. Wysocki, (Thu Jul 5, 10:09 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Jeremy Maitin-Shepard, (Thu Jul 5, 12:06 pm)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Rafael J. Wysocki, (Thu Jul 5, 10:59 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Rafael J. Wysocki, (Tue Jul 3, 11:22 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Rafael J. Wysocki, (Tue Jul 3, 10:51 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Tue Jul 3, 7:45 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Tue Jul 3, 7:44 am)
Re: [linux-pm] Re: [PATCH] Remove process freezer from suspe..., Benjamin Herrenschmidt, (Tue Jul 3, 7:40 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 1:51 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 5:16 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Rafael J. Wysocki, (Tue Jul 3, 11:09 am)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 5:20 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 5:56 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 7:08 pm)
Re: [PATCH] Remove process freezer from suspend to RAM pathway, Benjamin Herrenschmidt, (Tue Jul 3, 5:35 pm)
Re: [linux-pm] [PATCH] Remove process freezer from suspend t..., Benjamin Herrenschmidt, (Tue Jul 3, 1:49 am)