* Re: [Bugme-new] [Bug 10915] New: echo min_power > /sys/class/scsi_host/host0/active_mode causes problem
2008-06-16 2:00 ` James Bottomley
@ 2008-06-16 4:51 ` FUJITA Tomonori
2008-06-16 12:48 ` Andi Kleen
1 sibling, 0 replies; 4+ messages in thread
From: FUJITA Tomonori @ 2008-06-16 4:51 UTC (permalink / raw)
To: James.Bottomley; +Cc: akpm, linux-scsi, bugme-daemon, cijoml
On Sun, 15 Jun 2008 21:00:10 -0500
James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> On Sun, 2008-06-15 at 18:01 -0700, Andrew Morton wrote:
> > On Sun, 15 Jun 2008 01:52:26 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:
> >
> > > http://bugzilla.kernel.org/show_bug.cgi?id=10915
> > >
> > > Summary: echo min_power > /sys/class/scsi_host/host0/active_mode
> > > causes problem
> > > Product: File System
> > > Version: 2.5
> > > KernelVersion: 2.6.25.6
> > > Platform: All
> > > OS/Version: Linux
> > > Tree: Mainline
> > > Status: NEW
> > > Severity: normal
> > > Priority: P1
> > > Component: SysFS
> > > AssignedTo: greg@kroah.com
> > > ReportedBy: cijoml@volny.cz
> > >
> > >
> > > Latest working kernel version: unknown
> > > Earliest failing kernel version: unknown
> > > Distribution: Debian testing
> > > Hardware Environment: HP Compaq 6910p
> > > Software Environment: Debian testing, sysfs
> > > Problem Description:
> > >
> > > In accident I proceed
> > > echo min_power > /sys/class/scsi_host/host0/active_mode
> > >
> > > which causes HIGH cpu load, echo wasn't killable so reboot was only solution :(
> > >
> > > Steps to reproduce:
> > > proceed command
> >
> > For reasons which escape me, there is no description text in bugzilla
> > for this report, yet the reporter entered some.
> >
> > Anyway. Could someone please refile this under scsi? Or fix the bug ;)
>
> Um ... actually, maybe not. The active_mode file is read only (it has a
> NULL store method). It's designed to show what mode the host is
> activated in "initiator", "target" (or both or unknown). If echoing
> something to a read only sysfs file with no actual store method is
> causing this behaviour, the root cause has to be somewhere in sysfs.
This bug doesn't happen with the latest git so I guess that the root
cause was fixed, which can't handle the NULL store method properly.
But I think that it would be better to set active_mode and
support_mode files to read-only (though in the future, active_mode
would be changeable for a dual-mode driver).
> However, since the file has nothing to do with power saving ... unless
> some driver I can't find is trying to duplicate it, so there's no reason
> to try to echo "min_power" to it, so some of the details on this report
> might bear further investigation ...
I guess that he intended to echo "min_power" to
link_power_management_policy file.
=
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Subject: [PATCH] set active_mode and support_mode sysfs files to read-only
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
drivers/scsi/scsi_sysfs.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 93d2b67..01191bb 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -227,7 +227,7 @@ show_shost_supported_mode(struct device *dev, struct device_attribute *attr,
return show_shost_mode(supported_mode, buf);
}
-static DEVICE_ATTR(supported_mode, S_IRUGO | S_IWUSR, show_shost_supported_mode, NULL);
+static DEVICE_ATTR(supported_mode, S_IRUGO, show_shost_supported_mode, NULL);
static ssize_t
show_shost_active_mode(struct device *dev,
@@ -241,7 +241,7 @@ show_shost_active_mode(struct device *dev,
return show_shost_mode(shost->active_mode, buf);
}
-static DEVICE_ATTR(active_mode, S_IRUGO | S_IWUSR, show_shost_active_mode, NULL);
+static DEVICE_ATTR(active_mode, S_IRUGO, show_shost_active_mode, NULL);
shost_rd_attr(unique_id, "%u\n");
shost_rd_attr(host_busy, "%hu\n");
--
1.5.5.GIT
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [Bugme-new] [Bug 10915] New: echo min_power > /sys/class/scsi_host/host0/active_mode causes problem
2008-06-16 2:00 ` James Bottomley
2008-06-16 4:51 ` FUJITA Tomonori
@ 2008-06-16 12:48 ` Andi Kleen
1 sibling, 0 replies; 4+ messages in thread
From: Andi Kleen @ 2008-06-16 12:48 UTC (permalink / raw)
To: James Bottomley; +Cc: Andrew Morton, linux-scsi, bugme-daemon, cijoml
James Bottomley <James.Bottomley@HansenPartnership.com> writes:
>
> Um ... actually, maybe not. The active_mode file is read only (it has a
> NULL store method). It's designed to show what mode the host is
> activated in "initiator", "target" (or both or unknown). If echoing
> something to a read only sysfs file with no actual store method is
> causing this behaviour, the root cause has to be somewhere in sysfs.
>
> However, since the file has nothing to do with power saving ... unless
> some driver I can't find is trying to duplicate it, so there's no reason
> to try to echo "min_power" to it, so some of the details on this report
> might bear further investigation ...
I remember hitting something like this in the past when write() returned 0.
Some versions of echo loop in this case.
-Andi
^ permalink raw reply [flat|nested] 4+ messages in thread