swsusp: Use platform mode by default

It has been reported that on some systems the functionality after a resume from disk is limited if the system is simply powered off during the suspend instead of using the ACPI S4 suspend (aka platform mode).

Unfortunately the default is currently to power off the system during the suspend so the users of these systems experience problems after the resume if they don't switch to the platform mode explicitly. This patch makes swsusp use the platform mode by default to avoid such situations.

Signed-off-by Rafael J. Wysocki <[email protected]>

---

Index: linux-2.6.19-rc4-mm1/kernel/power/disk.c
===================================================================

kernel/power/disk.c +0 -0

@@ -62,9 +62,11 @@ static void power_down(suspend_disk_meth
 

It has been reported that on some systems the functionality after a resume from disk is limited if the system is simply powered off during the suspend instead of using the ACPI S4 suspend (aka platform mode).

Unfortunately the default is currently to power off the system during the suspend so the users of these systems experience problems after the resume if they don't switch to the platform mode explicitly. This patch makes swsusp use the platform mode by default to avoid such situations.

Signed-off-by Rafael J. Wysocki <[email protected]>

It has been reported that on some systems the functionality after a resume from disk is limited if the system is simply powered off during the suspend instead of using the ACPI S4 suspend (aka platform mode).

Unfortunately the default is currently to power off the system during the suspend so the users of these systems experience problems after the resume if they don't switch to the platform mode explicitly. This patch makes swsusp use the platform mode by default to avoid such situations.

Signed-off-by Rafael J. Wysocki <[email protected]>

---
 kernel/power/disk.c |    8 +++++---
 kernel/power/main.c |    2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

Index: linux-2.6.19-rc4-mm1/kernel/power/main.c
===================================================================

kernel/power/main.c +1 -1

@@ -29,7 +29,7 @@
 DECLARE_MUTEX(pm_sem);
 
 struct pm_ops *pm_ops;
-suspend_disk_method_t pm_disk_mode = PM_DISK_SHUTDOWN;
+suspend_disk_method_t pm_disk_mode = PM_DISK_PLATFORM;
 
 /**
  *	pm_set_ops - Set the global power method table. 

Index: linux-2.6.19-rc4-mm1/kernel/power/disk.c
===================================================================

kernel/power/disk.c +5 -4

@@ -62,9 +62,11 @@ static void power_down(suspend_disk_meth
 
 	switch(mode) {
 	case PM_DISK_PLATFORM:
-		kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
-		error = pm_ops->enter(PM_SUSPEND_DISK);
-		break;
+		if (pm_ops && pm_ops->enter) {
+			kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
+			error = pm_ops->enter(PM_SUSPEND_DISK);
+			break;
+		}
 	case PM_DISK_SHUTDOWN:
 		kernel_power_off();
 		break;
-

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Applied.

thanks,
-Len

Quoted 48 lines · Rafael J. Wysocki

It has been reported that on some systems the functionality after a resume from disk is limited if the system is simply powered off during the suspend instead of using the ACPI S4 suspend (aka platform mode).

Unfortunately the default is currently to power off the system during the suspend so the users of these systems experience problems after the resume if they don't switch to the platform mode explicitly. This patch makes swsusp use the platform mode by default to avoid such situations.

Signed-off-by Rafael J. Wysocki <[email protected]>

---
 kernel/power/disk.c |    8 +++++---
 kernel/power/main.c |    2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

Index: linux-2.6.19-rc4-mm1/kernel/power/main.c
===================================================================

kernel/power/main.c +1 -1

@@ -29,7 +29,7 @@
 DECLARE_MUTEX(pm_sem);
 
 struct pm_ops *pm_ops;
-suspend_disk_method_t pm_disk_mode = PM_DISK_SHUTDOWN;
+suspend_disk_method_t pm_disk_mode = PM_DISK_PLATFORM;
 
 /**
  *   pm_set_ops - Set the global power method table.

Index: linux-2.6.19-rc4-mm1/kernel/power/disk.c
===================================================================

kernel/power/disk.c +5 -4

@@ -62,9 +62,11 @@ static void power_down(suspend_disk_meth
 
      switch(mode) {
      case PM_DISK_PLATFORM:
-             kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
-             error = pm_ops->enter(PM_SUSPEND_DISK);
-             break;
+             if (pm_ops && pm_ops->enter) {
+                     kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
+                     error = pm_ops->enter(PM_SUSPEND_DISK);
+                     break;
+             }
      case PM_DISK_SHUTDOWN:
              kernel_power_off();
              break;
-

Hello,

(This patch is merged in 2.6.20 as commit
9185cfa92507d07ac787bc73d06c42222eec7239)

With this patch, my desktop no longer powers off after hibernate(8). It just reboots.

This user land fix can restore the old behavior:
echo shutdown > /sys/power/disk

The commit causes user land breakage. Is this behavior on purpose?

Quoted 54 lines

Applied.

thanks,
-Len

Quoted 48 lines · Rafael J. Wysocki

It has been reported that on some systems the functionality after a resume from disk is limited if the system is simply powered off during the suspend instead of using the ACPI S4 suspend (aka platform mode).

Unfortunately the default is currently to power off the system during the suspend so the users of these systems experience problems after the resume if they don't switch to the platform mode explicitly. This patch makes swsusp use the platform mode by default to avoid such situations.

Signed-off-by Rafael J. Wysocki <[email protected]>

---
 kernel/power/disk.c |    8 +++++---
 kernel/power/main.c |    2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

Index: linux-2.6.19-rc4-mm1/kernel/power/main.c
===================================================================

kernel/power/main.c +1 -1

@@ -29,7 +29,7 @@
 DECLARE_MUTEX(pm_sem);
 
 struct pm_ops *pm_ops;
-suspend_disk_method_t pm_disk_mode = PM_DISK_SHUTDOWN;
+suspend_disk_method_t pm_disk_mode = PM_DISK_PLATFORM;
 
 /**
  *   pm_set_ops - Set the global power method table.

Index: linux-2.6.19-rc4-mm1/kernel/power/disk.c
===================================================================

kernel/power/disk.c +5 -4

@@ -62,9 +62,11 @@ static void power_down(suspend_disk_meth
 
      switch(mode) {
      case PM_DISK_PLATFORM:
-             kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
-             error = pm_ops->enter(PM_SUSPEND_DISK);
-             break;
+             if (pm_ops && pm_ops->enter) {
+                     kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
+                     error = pm_ops->enter(PM_SUSPEND_DISK);
+                     break;
+             }
      case PM_DISK_SHUTDOWN:
              kernel_power_off();
              break;
-

We're working on fixing the breakage, but currently it's difficult, because none of my testboxes has problems with the 'platform' hibernation and I cannot reproduce the reported issues.

Quoted 4 lines · Rafael J. Wysocki

We're working on fixing the breakage, but currently it's difficult, because none of my testboxes has problems with the 'platform' hibernation and I cannot reproduce the reported issues.

The rule for anything ACPI-related has been: no regressions.

It doesn't matter if something fixes 10 boxes, if it breaks a single one, it's going to get reverted.

We had much too much of the "two steps forward, one step back" dance with ACPI a few years ago, which is the reason that rule got installed (and which is why it's ACPI-only: in some other subsystems we accept the fact that sometimes we don't know how to fix some hardware issue, but the new situation is at least better than the old one).

I agree that it can be aggravating to know that you can fix a problem for some people, but then being limited by the fact that it breaks for others. But beign able to *rely* on something that used to work is just too important, and with ACPI, you can never make a good judgement of which way works better (since it really just depends on some random firmware issues that we have zero visibility into).

Also, quite often, it may *seem* like something fixes more boxes than it breaks, but it's because people report *breakage* only, and then a few months later it turns out that it's exactly the other way around: now it's a hundred people who report breakage with the *new* code, and the reason people thought it fixed more than it broke was that the people for whom the old code worked fine obviously never reported it!

So this is why "a single regression is considered more important than ten fixes" - because a single regressionr report tends to actually be just the first indication of a lot of people who simply haven't tested the new code yet! People for whom the old code is broken are more likely to test new things.

So I'd just suggest changing the default back to PM_DISK_SHUTDOWN (but leave the "pm_ops->enter" testing in place - ie not reverting the other commits in the series).

Just to clarify, the change in question isn't new. It was introduced by the commit 9185cfa92507d07ac787bc73d06c42222eec7239 before 2.6.20, at Seife's request and with Pavel's acceptance.

Quoted 3 lines

Just to clarify, the change in question isn't new. It was introduced by the commit 9185cfa92507d07ac787bc73d06c42222eec7239 before 2.6.20, at Seife's request and with Pavel's acceptance.

Ok, if it's that old, we migt as leave it in. Clearly there weren't many regressions, and this isn't a case of other monsters lurking behind a lack of testers.

Quoted 4 lines · Rafael J. Wysocki

Just to clarify, the change in question isn't new. It was introduced by the commit 9185cfa92507d07ac787bc73d06c42222eec7239 before 2.6.20, at Seife's request and with Pavel's acceptance.

Ok, if it's that old, we migt as leave it in. Clearly there weren't many regressions, and this isn't a case of other monsters lurking behind a lack of testers.

Quoted 11 lines · Linus Torvalds

Quoted 4 lines · Rafael J. Wysocki

Just to clarify, the change in question isn't new. It was introduced by the commit 9185cfa92507d07ac787bc73d06c42222eec7239 before 2.6.20, at Seife's request and with Pavel's acceptance.

Ok, if it's that old, we migt as leave it in. Clearly there weren't many regressions, and this isn't a case of other monsters lurking behind a lack of testers.

I pushed for this since on ACPI machines, "platform" is the right thing to do, and i still think it will only break on machines that have a broken ACPI BIOS. (Are there machines with broken ACPI BIOS around? ;-)

Your additional "fall back to shutdown if !(ops)"-fix looks very sane, however, and is definitely a good idea.

The key point is "fall back to shutdown _only_ if !ops, otherwise don't touch hibernation_mode". And that solves my problem.

Quoted 7 lines · Linus Torvalds

Quoted 3 lines · Rafael J. Wysocki

We're working on fixing the breakage, but currently it's difficult, because none of my testboxes has problems with the 'platform' hibernation and I cannot reproduce the reported issues.

The rule for anything ACPI-related has been: no regressions.

It doesn't matter if something fixes 10 boxes, if it breaks a single one, it's going to get reverted.

[Well, I think I should stop explaining decisions that weren't mine. Yet, I feel responsible for patches that I sign-off.]

Just to clarify, the change in question isn't new. It was introduced by the commit 9185cfa92507d07ac787bc73d06c42222eec7239 before 2.6.20, at Seife's request and with Pavel's acceptance.

Quoted 9 lines

We had much too much of the "two steps forward, one step back" dance with ACPI a few years ago, which is the reason that rule got installed (and which is why it's ACPI-only: in some other subsystems we accept the fact that sometimes we don't know how to fix some hardware issue, but the new situation is at least better than the old one).

I agree that it can be aggravating to know that you can fix a problem for some people, but then being limited by the fact that it breaks for others. But beign able to *rely* on something that used to work is just too important, and with ACPI, you can never make a good judgement of which way works better (since it really just depends on some random firmware issues that we have zero visibility into).

Also, quite often, it may *seem* like something fixes more boxes than it breaks, but it's because people report *breakage* only, and then a few months later it turns out that it's exactly the other way around: now it's a hundred people who report breakage with the *new* code, and the reason people thought it fixed more than it broke was that the people for whom the old code worked fine obviously never reported it!

So this is why "a single regression is considered more important than ten fixes" - because a single regressionr report tends to actually be just the first indication of a lot of people who simply haven't tested the new code yet! People for whom the old code is broken are more likely to test new things.

So I'd just suggest changing the default back to PM_DISK_SHUTDOWN (but leave the "pm_ops->enter" testing in place - ie not reverting the other commits in the series).

The series actually preserves the 2.6.20/21 behavior. By defaulting back to PM_DISK_SHUTDOWN, we'll cause some users for whom 2.6.20 and 2.6.21 work to report this change as a regression, so please let me avoid making this decision (I'm not the maintainer of the hibernation code after all).

The problem is that we don't know about regressions until somebody reports them and if that happens after two affected kernel releases, what should we do?

Quoted 4 lines · Rafael J. Wysocki

We're working on fixing the breakage, but currently it's difficult, because none of my testboxes has problems with the 'platform' hibernation and I cannot reproduce the reported issues.

The rule for anything ACPI-related has been: no regressions.

It doesn't matter if something fixes 10 boxes, if it breaks a single one, it's going to get reverted.

We had much too much of the "two steps forward, one step back" dance with ACPI a few years ago, which is the reason that rule got installed (and which is why it's ACPI-only: in some other subsystems we accept the fact that sometimes we don't know how to fix some hardware issue, but the new situation is at least better than the old one).

I agree that it can be aggravating to know that you can fix a problem for some people, but then being limited by the fact that it breaks for others. But beign able to *rely* on something that used to work is just too important, and with ACPI, you can never make a good judgement of which way works better (since it really just depends on some random firmware issues that we have zero visibility into).

Also, quite often, it may *seem* like something fixes more boxes than it breaks, but it's because people report *breakage* only, and then a few months later it turns out that it's exactly the other way around: now it's a hundred people who report breakage with the *new* code, and the reason people thought it fixed more than it broke was that the people for whom the old code worked fine obviously never reported it!

So this is why "a single regression is considered more important than ten fixes" - because a single regressionr report tends to actually be just the first indication of a lot of people who simply haven't tested the new code yet! People for whom the old code is broken are more likely to test new things.

So I'd just suggest changing the default back to PM_DISK_SHUTDOWN (but leave the "pm_ops->enter" testing in place - ie not reverting the other commits in the series).

The patch would look something like this. Coywolf, does this fix it for you?

Linus

---
 kernel/power/disk.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

kernel/power/disk.c +3 -3

index b5f0543..f6aa06e 100644
@@ -60,9 +60,9 @@ void hibernation_set_ops(struct hibernation_ops *ops)
        }
        mutex_lock(&pm_mutex);
        hibernation_ops = ops;
-       if (ops)
-               hibernation_mode = HIBERNATION_PLATFORM;
-       else if (hibernation_mode == HIBERNATION_PLATFORM)
+
+       /* Turn off HIBERNATION_PLATFORM if we no longer have any platform ops */
+       if (!ops && hibernation_mode == HIBERNATION_PLATFORM)
                hibernation_mode = HIBERNATION_SHUTDOWN;
 
        mutex_unlock(&pm_mutex);

Quoted 39 lines · Linus Torvalds

Quoted 4 lines · Rafael J. Wysocki

We're working on fixing the breakage, but currently it's difficult, because none of my testboxes has problems with the 'platform' hibernation and I cannot reproduce the reported issues.

The rule for anything ACPI-related has been: no regressions.

It doesn't matter if something fixes 10 boxes, if it breaks a single one, it's going to get reverted.

We had much too much of the "two steps forward, one step back" dance with ACPI a few years ago, which is the reason that rule got installed (and which is why it's ACPI-only: in some other subsystems we accept the fact that sometimes we don't know how to fix some hardware issue, but the new situation is at least better than the old one).

I agree that it can be aggravating to know that you can fix a problem for some people, but then being limited by the fact that it breaks for others. But beign able to *rely* on something that used to work is just too important, and with ACPI, you can never make a good judgement of which way works better (since it really just depends on some random firmware issues that we have zero visibility into).

Also, quite often, it may *seem* like something fixes more boxes than it breaks, but it's because people report *breakage* only, and then a few months later it turns out that it's exactly the other way around: now it's a hundred people who report breakage with the *new* code, and the reason people thought it fixed more than it broke was that the people for whom the old code worked fine obviously never reported it!

So this is why "a single regression is considered more important than ten fixes" - because a single regressionr report tends to actually be just the first indication of a lot of people who simply haven't tested the new code yet! People for whom the old code is broken are more likely to test new things.

Quoted 7 lines

So I'd just suggest changing the default back to PM_DISK_SHUTDOWN (but leave the "pm_ops->enter" testing in place - ie not reverting the other commits in the series).

The patch would look something like this. Coywolf, does this fix it for you?

Yes, it fixes my problem.

(Sorry for this long delayed report. I didn't get the chance to test and reboot my box.)

This quick test explains me the problem that we should not set hibernation_mode to HIBERNATION_PLATFORM if it is not !ops". I will post a formal patch later.

kernel/power/disk.c +0 -0

index eb72255..8e52553 100644

Quoted 25 lines

Linus

---
 kernel/power/disk.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

kernel/power/disk.c +3 -3

index b5f0543..f6aa06e 100644
@@ -60,9 +60,9 @@ void hibernation_set_ops(struct hibernation_ops *ops)
        }
        mutex_lock(&pm_mutex);
        hibernation_ops = ops;
-       if (ops)
-               hibernation_mode = HIBERNATION_PLATFORM;
-       else if (hibernation_mode == HIBERNATION_PLATFORM)
+
+       /* Turn off HIBERNATION_PLATFORM if we no longer have any platform ops */
+       if (!ops && hibernation_mode == HIBERNATION_PLATFORM)
                hibernation_mode = HIBERNATION_SHUTDOWN;
 
        mutex_unlock(&pm_mutex);

Signature · 6 lines

Qi Yong
-
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Please read the FAQ at  http://www.tux.org/lkml/

Quoted 2 lines · Qi Yong

Quoted 1 line · Linus Torvalds

On Fri, 11 May 2007, Rafael J. Wysocki wrote:

please apply.

Signed-off-by Qi Yong <[email protected]>

---

kernel/power/disk.c +0 -1

index eb72255..95b66ee 100644
@@ -61,9 +61,11 @@ void hibernation_set_ops(struct hibernation_ops *ops)
 	}
 	mutex_lock(&pm_mutex);
 	hibernation_ops = ops;
-	if (ops)