Regression in 2.6.28-rc and 2.6.27-stable - hibernate related

["Fabio Comolli" <fabio.comolli@gmail.com>]

Hi.
As the subject says, I have a strange regression in latest git.
Sometimes resume from hibernating hangs _after_ the resume stage.
When the problem happens I usually have to powercycle my laptop.

The system managed to recover from the hang only twice and this time I
found in the logs:

Nov 23 16:43:14 hawking kernel: sd 0:0:0:0: [sda] Starting disk
Nov 23 16:43:14 hawking kernel: Restarting tasks ... done.
Nov 23 16:43:52 hawking kernel: ata1.01: exception Emask 0x0 SAct 0x0
SErr 0x0 action 0x6 frozen
Nov 23 16:43:52 hawking kernel: ata1.01: cmd
a0/00:00:00:00:00/00:00:00:00:00/b0 tag 0
Nov 23 16:43:52 hawking kernel:          cdb 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
Nov 23 16:43:52 hawking kernel:          res
40/00:03:00:00:00/00:00:00:00:00/b0 Emask 0x4 (timeout)
Nov 23 16:43:52 hawking kernel: ata1.01: status: { DRDY }
Nov 23 16:43:52 hawking kernel: ata1: soft resetting link
Nov 23 16:43:57 hawking kernel: ata1.01: qc timeout (cmd 0xa1)
Nov 23 16:43:57 hawking kernel: ata1.01: failed to IDENTIFY (I/O
error, err_mask=0x4)
Nov 23 16:43:57 hawking kernel: ata1.01: revalidation failed (errno=-5)
Nov 23 16:43:57 hawking kernel: ata1: soft resetting link
Nov 23 16:44:08 hawking kernel: ata1.01: qc timeout (cmd 0xa1)
Nov 23 16:44:08 hawking kernel: ata1.01: failed to IDENTIFY (I/O
error, err_mask=0x4)
Nov 23 16:44:08 hawking kernel: ata1.01: revalidation failed (errno=-5)
Nov 23 16:44:08 hawking kernel: ata1: soft resetting link
Nov 23 16:44:38 hawking kernel: ata1.00: configured for UDMA/100
Nov 23 16:44:38 hawking kernel: ata1.01: configured for MWDMA2
Nov 23 16:44:38 hawking kernel: ata1: EH complete
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] 156301488 512-byte
hardware sectors: (80.0 GB/74.5 GiB)
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] Write Protect is off
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] Write cache:
enabled, read cache: enabled, doesn't support DPO or FUA
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] 156301488 512-byte
hardware sectors: (80.0 GB/74.5 GiB)
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] Write Protect is off
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
Nov 23 16:44:39 hawking kernel: sd 0:0:0:0: [sda] Write cache:
enabled, read cache: enabled, doesn't support DPO or FUA

This problem:

* never happened in 2.6.27.4
* happened many times in 2.6.27.5 and .6
* never happened in 2.6.27.7
* happened the first time with the current -rc series just now (the
logs are related to this one)

This is the first 2.6.28-rc kernel I tried.

I have to say that my kernel is tainted (fglrx and cisco_ipsec) but I
also managed to replicate the hangs also with non-tainted ones.

I already tried some bisection between 2.6.27.4 and 2.6.27.5 but with
no result, probably because I marked as "good" kernel that weren't
good at all. Unfortunately this bug happens really at random times.

During the bisection I always used non-tainted kernels.

If anyone has ideas, I can provide some more data; I can also try
another bisection series but I think it would take very long to get
some good results (I mean, some days of testing between two different
kernels just to reproduce the bug).

Regards,
Fabio