[PATCH v1] PM: sleep: Allow pm_restrict_gfp_mask() stacking

[PATCH v1] PM: sleep: Allow pm_restrict_gfp_mask() stacking

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Allow pm_restrict_gfp_mask() to be called many times in a row to avoid
issues with calling dpm_suspend_start() when the GFP mask has been
already restricted.

Only the first invocation of pm_restrict_gfp_mask() will actually
restrict the GFP mask and the subsequent calls will warn if there is
a mismatch between the expected allowed GFP mask and the actual one.

Moreover, if pm_restrict_gfp_mask() is called many times in a row,
pm_restore_gfp_mask() needs to be called matching number of times in
a row to actually restore the GFP mask.  Calling it when the GFP mask
has not been restricted will cause it to warn.

This is necessary for the GFP mask restriction starting in
hibernation_snapshot() to continue throughout the entire hibernation
flow until it completes or it is aborted (either by a wakeup event or
by an error).

Fixes: 449c9c02537a1 ("PM: hibernate: Restrict GFP mask in hibernation_snapshot()")
Fixes: 469d80a3712c ("PM: hibernate: Fix hybrid-sleep")
Reported-by: Askar Safin <safinaskar@gmail.com>
Closes: https://lore.kernel.org/linux-pm/20251025050812.421905-1-safinaskar@gmail.com/
Link: https://lore.kernel.org/linux-pm/20251028111730.2261404-1-safinaskar@gmail.com/
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

This supersedes

https://lore.kernel.org/linux-pm/20251026033115.436448-1-superm1@kernel.org/

as it allows the GFP mask to be restricted across the entire hibernation path.

---
 kernel/power/hibernate.c |    4 ----
 kernel/power/main.c      |   22 +++++++++++++++++-----
 2 files changed, 17 insertions(+), 9 deletions(-)

--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -706,7 +706,6 @@ static void power_down(void)
 
 #ifdef CONFIG_SUSPEND
 	if (hibernation_mode == HIBERNATION_SUSPEND) {
-		pm_restore_gfp_mask();
 		error = suspend_devices_and_enter(mem_sleep_current);
 		if (!error)
 			goto exit;
@@ -746,9 +745,6 @@ static void power_down(void)
 		cpu_relax();
 
 exit:
-	/* Match the pm_restore_gfp_mask() call in hibernate(). */
-	pm_restrict_gfp_mask();
-
 	/* Restore swap signature. */
 	error = swsusp_unmark();
 	if (error)
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -31,23 +31,35 @@
  * held, unless the suspend/hibernate code is guaranteed not to run in parallel
  * with that modification).
  */
+static unsigned int saved_gfp_count;
 static gfp_t saved_gfp_mask;
 
 void pm_restore_gfp_mask(void)
 {
 	WARN_ON(!mutex_is_locked(&system_transition_mutex));
-	if (saved_gfp_mask) {
-		gfp_allowed_mask = saved_gfp_mask;
-		saved_gfp_mask = 0;
-	}
+
+	if (WARN_ON(!saved_gfp_count) || --saved_gfp_count)
+		return;
+
+	gfp_allowed_mask = saved_gfp_mask;
+	saved_gfp_mask = 0;
+
+	pm_pr_dbg("GFP mask restored\n");
 }
 
 void pm_restrict_gfp_mask(void)
 {
 	WARN_ON(!mutex_is_locked(&system_transition_mutex));
-	WARN_ON(saved_gfp_mask);
+
+	if (saved_gfp_count++) {
+		WARN_ON((saved_gfp_mask & ~(__GFP_IO | __GFP_FS)) != gfp_allowed_mask);
+		return;
+	}
+
 	saved_gfp_mask = gfp_allowed_mask;
 	gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);
+
+	pm_pr_dbg("GFP mask restricted\n");
 }
 
 unsigned int lock_system_sleep(void)

Re: [PATCH v1] PM: sleep: Allow pm_restrict_gfp_mask() stacking

[Mario Limonciello]

On 10/28/25 3:52 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Allow pm_restrict_gfp_mask() to be called many times in a row to avoid
> issues with calling dpm_suspend_start() when the GFP mask has been
> already restricted.
> 
> Only the first invocation of pm_restrict_gfp_mask() will actually
> restrict the GFP mask and the subsequent calls will warn if there is
> a mismatch between the expected allowed GFP mask and the actual one.
> 
> Moreover, if pm_restrict_gfp_mask() is called many times in a row,
> pm_restore_gfp_mask() needs to be called matching number of times in
> a row to actually restore the GFP mask.  Calling it when the GFP mask
> has not been restricted will cause it to warn.
> 
> This is necessary for the GFP mask restriction starting in
> hibernation_snapshot() to continue throughout the entire hibernation
> flow until it completes or it is aborted (either by a wakeup event or
> by an error).
> 
> Fixes: 449c9c02537a1 ("PM: hibernate: Restrict GFP mask in hibernation_snapshot()")
> Fixes: 469d80a3712c ("PM: hibernate: Fix hybrid-sleep")
> Reported-by: Askar Safin <safinaskar@gmail.com>
> Closes: https://lore.kernel.org/linux-pm/20251025050812.421905-1-safinaskar@gmail.com/
> Link: https://lore.kernel.org/linux-pm/20251028111730.2261404-1-safinaskar@gmail.com/
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Great idea.  Looks good to me, and it passes the S4 tests on my side.

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Tested-by: Mario Limonciello (AMD) <superm1@kernel.org>

> ---
> 
> This supersedes
> 
> https://lore.kernel.org/linux-pm/20251026033115.436448-1-superm1@kernel.org/
> 
> as it allows the GFP mask to be restricted across the entire hibernation path.
> 
> ---
>   kernel/power/hibernate.c |    4 ----
>   kernel/power/main.c      |   22 +++++++++++++++++-----
>   2 files changed, 17 insertions(+), 9 deletions(-)
> 
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -706,7 +706,6 @@ static void power_down(void)
>   
>   #ifdef CONFIG_SUSPEND
>   	if (hibernation_mode == HIBERNATION_SUSPEND) {
> -		pm_restore_gfp_mask();
>   		error = suspend_devices_and_enter(mem_sleep_current);
>   		if (!error)
>   			goto exit;
> @@ -746,9 +745,6 @@ static void power_down(void)
>   		cpu_relax();
>   
>   exit:
> -	/* Match the pm_restore_gfp_mask() call in hibernate(). */
> -	pm_restrict_gfp_mask();
> -
>   	/* Restore swap signature. */
>   	error = swsusp_unmark();
>   	if (error)
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -31,23 +31,35 @@
>    * held, unless the suspend/hibernate code is guaranteed not to run in parallel
>    * with that modification).
>    */
> +static unsigned int saved_gfp_count;
>   static gfp_t saved_gfp_mask;
>   
>   void pm_restore_gfp_mask(void)
>   {
>   	WARN_ON(!mutex_is_locked(&system_transition_mutex));
> -	if (saved_gfp_mask) {
> -		gfp_allowed_mask = saved_gfp_mask;
> -		saved_gfp_mask = 0;
> -	}
> +
> +	if (WARN_ON(!saved_gfp_count) || --saved_gfp_count)
> +		return;
> +
> +	gfp_allowed_mask = saved_gfp_mask;
> +	saved_gfp_mask = 0;
> +
> +	pm_pr_dbg("GFP mask restored\n");
>   }
>   
>   void pm_restrict_gfp_mask(void)
>   {
>   	WARN_ON(!mutex_is_locked(&system_transition_mutex));
> -	WARN_ON(saved_gfp_mask);
> +
> +	if (saved_gfp_count++) {
> +		WARN_ON((saved_gfp_mask & ~(__GFP_IO | __GFP_FS)) != gfp_allowed_mask);
> +		return;
> +	}
> +
>   	saved_gfp_mask = gfp_allowed_mask;
>   	gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);
> +
> +	pm_pr_dbg("GFP mask restricted\n");
>   }
>   
>   unsigned int lock_system_sleep(void)
> 
> 
> 

Re: [PATCH v1] PM: sleep: Allow pm_restrict_gfp_mask() stacking

[Rafael J. Wysocki]

On Wed, Oct 29, 2025 at 4:22 PM Mario Limonciello <superm1@kernel.org> wrote:
>
> On 10/28/25 3:52 PM, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Allow pm_restrict_gfp_mask() to be called many times in a row to avoid
> > issues with calling dpm_suspend_start() when the GFP mask has been
> > already restricted.
> >
> > Only the first invocation of pm_restrict_gfp_mask() will actually
> > restrict the GFP mask and the subsequent calls will warn if there is
> > a mismatch between the expected allowed GFP mask and the actual one.
> >
> > Moreover, if pm_restrict_gfp_mask() is called many times in a row,
> > pm_restore_gfp_mask() needs to be called matching number of times in
> > a row to actually restore the GFP mask.  Calling it when the GFP mask
> > has not been restricted will cause it to warn.
> >
> > This is necessary for the GFP mask restriction starting in
> > hibernation_snapshot() to continue throughout the entire hibernation
> > flow until it completes or it is aborted (either by a wakeup event or
> > by an error).
> >
> > Fixes: 449c9c02537a1 ("PM: hibernate: Restrict GFP mask in hibernation_snapshot()")
> > Fixes: 469d80a3712c ("PM: hibernate: Fix hybrid-sleep")
> > Reported-by: Askar Safin <safinaskar@gmail.com>
> > Closes: https://lore.kernel.org/linux-pm/20251025050812.421905-1-safinaskar@gmail.com/
> > Link: https://lore.kernel.org/linux-pm/20251028111730.2261404-1-safinaskar@gmail.com/
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Great idea.  Looks good to me, and it passes the S4 tests on my side.
>
> Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Tested-by: Mario Limonciello (AMD) <superm1@kernel.org>

Great, thanks!

Re: [PATCH v1] PM: sleep: Allow pm_restrict_gfp_mask() stacking

[Kenneth Crudup]

On 10/28/25 13:52, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Allow pm_restrict_gfp_mask() to be called many times in a row to avoid
> issues with calling dpm_suspend_start() when the GFP mask has been
> already restricted.
> 
> Only the first invocation of pm_restrict_gfp_mask() will actually
> restrict the GFP mask and the subsequent calls will warn if there is
> a mismatch between the expected allowed GFP mask and the actual one.
> 
> Moreover, if pm_restrict_gfp_mask() is called many times in a row,
> pm_restore_gfp_mask() needs to be called matching number of times in
> a row to actually restore the GFP mask.  Calling it when the GFP mask
> has not been restricted will cause it to warn.
> 
> This is necessary for the GFP mask restriction starting in
> hibernation_snapshot() to continue throughout the entire hibernation
> flow until it completes or it is aborted (either by a wakeup event or
> by an error).
> 
> Fixes: 449c9c02537a1 ("PM: hibernate: Restrict GFP mask in hibernation_snapshot()")
> Fixes: 469d80a3712c ("PM: hibernate: Fix hybrid-sleep")
> Reported-by: Askar Safin <safinaskar@gmail.com>
> Closes: https://lore.kernel.org/linux-pm/20251025050812.421905-1-safinaskar@gmail.com/
> Link: https://lore.kernel.org/linux-pm/20251028111730.2261404-1-safinaskar@gmail.com/
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> 
> This supersedes
> 
> https://lore.kernel.org/linux-pm/20251026033115.436448-1-superm1@kernel.org/
> 
> as it allows the GFP mask to be restricted across the entire hibernation path.

Tested-By: Kenneth R. Crudup <kenny@panix.com>

(Helgaas told me about "b4 shazam" and I've been applying all kinds of 
interesting patches willy-nilly lately :) )

> ---
>   kernel/power/hibernate.c |    4 ----
>   kernel/power/main.c      |   22 +++++++++++++++++-----
>   2 files changed, 17 insertions(+), 9 deletions(-)
> 
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -706,7 +706,6 @@ static void power_down(void)
>   
>   #ifdef CONFIG_SUSPEND
>   	if (hibernation_mode == HIBERNATION_SUSPEND) {
> -		pm_restore_gfp_mask();
>   		error = suspend_devices_and_enter(mem_sleep_current);
>   		if (!error)
>   			goto exit;
> @@ -746,9 +745,6 @@ static void power_down(void)
>   		cpu_relax();
>   
>   exit:
> -	/* Match the pm_restore_gfp_mask() call in hibernate(). */
> -	pm_restrict_gfp_mask();
> -
>   	/* Restore swap signature. */
>   	error = swsusp_unmark();
>   	if (error)
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -31,23 +31,35 @@
>    * held, unless the suspend/hibernate code is guaranteed not to run in parallel
>    * with that modification).
>    */
> +static unsigned int saved_gfp_count;
>   static gfp_t saved_gfp_mask;
>   
>   void pm_restore_gfp_mask(void)
>   {
>   	WARN_ON(!mutex_is_locked(&system_transition_mutex));
> -	if (saved_gfp_mask) {
> -		gfp_allowed_mask = saved_gfp_mask;
> -		saved_gfp_mask = 0;
> -	}
> +
> +	if (WARN_ON(!saved_gfp_count) || --saved_gfp_count)
> +		return;
> +
> +	gfp_allowed_mask = saved_gfp_mask;
> +	saved_gfp_mask = 0;
> +
> +	pm_pr_dbg("GFP mask restored\n");
>   }
>   
>   void pm_restrict_gfp_mask(void)
>   {
>   	WARN_ON(!mutex_is_locked(&system_transition_mutex));
> -	WARN_ON(saved_gfp_mask);
> +
> +	if (saved_gfp_count++) {
> +		WARN_ON((saved_gfp_mask & ~(__GFP_IO | __GFP_FS)) != gfp_allowed_mask);
> +		return;
> +	}
> +
>   	saved_gfp_mask = gfp_allowed_mask;
>   	gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);
> +
> +	pm_pr_dbg("GFP mask restricted\n");
>   }
>   
>   unsigned int lock_system_sleep(void)
> 
> 
> 
> 

-- 
Kenneth R. Crudup / Sr. SW Engineer, Scott County Consulting, Orange 
County CA