Re: [Sound-open-firmware] [PATCH v8 2/3] freezer: refactor pm_freezing into a function.

Hi Rafael

On Fri, 2 Dec 2022 at 18:48, Rafael J. Wysocki rafael@kernel.org wrote:

On Thu, Dec 1, 2022 at 12:08 PM Ricardo Ribalda ribalda@chromium.org wrote:

...

Add a way to let the drivers know if the processes are frozen.

This is needed by drivers that are waiting for processes to end on their shutdown path.

Convert pm_freezing into a function and export it, so it can be used by drivers that are either built-in or modules.

Cc: stable@vger.kernel.org Fixes: 83bfc7e793b5 ("ASoC: SOF: core: unregister clients and machine drivers in .shutdown") Signed-off-by: Ricardo Ribalda ribalda@chromium.org

Why can't you export the original pm_freezing variable and why is this fixing anything?

Because then any module will be able to modify the content of the variable.

The Fixes: is because the last patch on the set is doing a real fix. If you only cherry-pick the last patch on a stable branch, the build will fail. (Also, the zero-day builder complains)

Anyway, I think we can hold this patch for a bit. The snd people are discussing if this the way to handle it, or if we should handle .shutdown in a different way.

Thanks!

...

---

include/linux/freezer.h | 3 ++- kernel/freezer.c | 3 +-- kernel/power/process.c | 24 ++++++++++++++++++++---- 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/linux/freezer.h b/include/linux/freezer.h index b303472255be..3413c869d68b 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -13,7 +13,7 @@ #ifdef CONFIG_FREEZER DECLARE_STATIC_KEY_FALSE(freezer_active);

-extern bool pm_freezing; /* PM freezing in effect */ +bool pm_freezing(void); extern bool pm_nosig_freezing; /* PM nosig freezing in effect */

/* @@ -80,6 +80,7 @@ static inline int freeze_processes(void) { return -ENOSYS; } static inline int freeze_kernel_threads(void) { return -ENOSYS; } static inline void thaw_processes(void) {} static inline void thaw_kernel_threads(void) {} +static inline bool pm_freezing(void) { return false; }

static inline bool try_to_freeze(void) { return false; }

diff --git a/kernel/freezer.c b/kernel/freezer.c index 4fad0e6fca64..2d3530ebdb7e 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -20,7 +20,6 @@ EXPORT_SYMBOL(freezer_active);

• indicate whether PM freezing is in effect, protected by
• system_transition_mutex

*/ -bool pm_freezing; bool pm_nosig_freezing;

/* protects freezing and frozen transitions */ @@ -46,7 +45,7 @@ bool freezing_slow_path(struct task_struct *p) if (pm_nosig_freezing || cgroup_freezing(p)) return true;

•   if (pm_freezing && !(p->flags & PF_KTHREAD))
  

•   if (pm_freezing() && !(p->flags & PF_KTHREAD))
            return true;
  
    return false;
  

diff --git a/kernel/power/process.c b/kernel/power/process.c index ddd9988327fe..8a4d0e2c8c20 100644 --- a/kernel/power/process.c +++ b/kernel/power/process.c @@ -108,6 +108,22 @@ static int try_to_freeze_tasks(bool user_only) return todo ? -EBUSY : 0; }

+/*

• • Indicate whether PM freezing is in effect, protected by
• • system_transition_mutex.
• */

+static bool pm_freezing_internal;

+/**

• • pm_freezing - indicate whether PM freezing is in effect.
• */

+bool pm_freezing(void) +{

•   return pm_freezing_internal;
  

+} +EXPORT_SYMBOL(pm_freezing);

Use EXPORT_SYMBOL_GPL() instead, please.

...

/**

• freeze_processes - Signal user space processes to enter the refrigerator.
• The current thread will not be frozen. The same process that calls

@@ -126,12 +142,12 @@ int freeze_processes(void) /* Make sure this task doesn't get frozen */ current->flags |= PF_SUSPEND_TASK;

•   if (!pm_freezing)
  

•   if (!pm_freezing())
            static_branch_inc(&freezer_active);
  
    pm_wakeup_clear(0);
    pr_info("Freezing user space processes ... ");
  

•   pm_freezing = true;
  

•   pm_freezing_internal = true;
    error = try_to_freeze_tasks(true);
    if (!error) {
            __usermodehelper_set_disable_depth(UMH_DISABLED);
  

@@ -187,9 +203,9 @@ void thaw_processes(void) struct task_struct *curr = current;

    trace_suspend_resume(TPS("thaw_processes"), 0, true);

•   if (pm_freezing)
  

•   if (pm_freezing())
            static_branch_dec(&freezer_active);
  

•   pm_freezing = false;
  

•   pm_freezing_internal = false;
    pm_nosig_freezing = false;
  
    oom_killer_enable();
  
  

--

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-- Ricardo Ribalda