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SubjectRe: 3.4.0-02580-g72c04af regression on sparc64 - partitions not recognized
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On Wed, 2012-05-23 at 23:56 +0100, James Bottomley wrote:
> On Wed, 2012-05-23 at 14:04 -0400, David Miller wrote:
> > From: Meelis Roos <mroos@linux.ee>
> > Date: Wed, 23 May 2012 19:46:46 +0300 (EEST)
> >
> > CC:'ing interested parties.
> >
> > >> > Just tested 3.4.0-02580-g72c04af on about 10 machines. While most of
> > >> > them work (including 3 different sparc64 machines with real scsi disks),
> > >> > Sun Netra X1 with pata_ali and IDE disk consistently fails to boot. sda
> > >> > is recognized but no partitions. 3.3.0 works fine, as did something
> > >> > around 3.4-rc7 (plain 3.4 not tested yet). No other IDE machines tested
> > >> > yet since I have none with remote console at the moment.
> > >>
> > >> If 3.4.0-final is OK, start bisecting from v3.4.0 until 72c04af. One
> > >> possibility could be the sparc64 NOBOOTMEM conversion that went into
> > >> the merge window.
> > >
> > > Bisecting leads to this commit:
> > >
> > > a7a20d103994fd760766e6c9d494daa569cbfe06 is the first bad commit
> > > commit a7a20d103994fd760766e6c9d494daa569cbfe06
> > > Author: Dan Williams <dan.j.williams@intel.com>
> > > Date: Thu Mar 22 17:05:11 2012 -0700
> > >
> > > [SCSI] sd: limit the scope of the async probe domain
>
> My theory is that this is an init problem: The assumption in a lot of
> our code is that async_synchronize_full() waits for everything ... even
> the domain specific async schedules, which isn't true.
>
> The code in init that makes this assumption is wait_for_device_probe().
> There's also a fun async_synchronize_full() in init_post() that assumes
> it can free the init memory after, which would fail badly if anything in
> init used an async domain.
>
> So either we fix the assumptions or we can't use domain specific async
> schedules.
>

Hm, we already have cases of code not trusting the semantics of
wait_for_device_probe(), especially as it relates to async scanning like
in kernel/power/hibernate.c:

/*
* Some device discovery might still be in progress; we need
* to wait for this to finish.
*/
wait_for_device_probe();

if (resume_wait) {
while ((swsusp_resume_device = name_to_dev_t(resume_file)) == 0)
msleep(10);
async_synchronize_full();
}

/*
* We can't depend on SCSI devices being available after loading
* one of their modules until scsi_complete_async_scans() is
* called and the resume device usually is a SCSI one.
*/
scsi_complete_async_scans();


...so it seems scsi_complete_async_scans() should take care to flush sd
probe actions as well... here is a test patch:

--- snip ---

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 8906557..05a92d3 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -141,13 +141,13 @@ struct async_scan_data {
* started scanning after this function was called may or may not have
* finished.
*/
-int scsi_complete_async_scans(void)
+static void __scsi_complete_async_scans(void)
{
struct async_scan_data *data;

do {
if (list_empty(&scanning_hosts))
- return 0;
+ return;
/* If we can't get memory immediately, that's OK. Just
* sleep a little. Even if we never get memory, the async
* scans will finish eventually.
@@ -181,6 +181,13 @@ int scsi_complete_async_scans(void)
spin_unlock(&async_scan_lock);

kfree(data);
+}
+
+int scsi_complete_async_scans(void)
+{
+ __scsi_complete_async_scans();
+ async_synchronize_full_domain(&scsi_sd_probe_domain);
+
return 0;
}




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