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Date: Mon, 5 Dec 2022 13:05:29 +0100
From: Ricardo Ribalda <ribalda@...omium.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Juergen Gross <jgross@...e.com>, Mark Brown <broonie@...nel.org>,
Chromeos Kdump <chromeos-kdump@...gle.com>,
Daniel Baluta <daniel.baluta@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Len Brown <len.brown@...el.com>,
Ard Biesheuvel <ardb@...nel.org>,
Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Nicholas Piggin <npiggin@...il.com>,
Michael Ellerman <mpe@...erman.id.au>,
Eric Biederman <ebiederm@...ssion.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Jaroslav Kysela <perex@...ex.cz>,
Joel Fernandes <joel@...lfernandes.org>,
Liam Girdwood <lgirdwood@...il.com>,
Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
Pavel Machek <pavel@....cz>,
Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
Steven Rostedt <rostedt@...dmis.org>,
"K. Y. Srinivasan" <kys@...rosoft.com>,
Ingo Molnar <mingo@...hat.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Dexuan Cui <decui@...rosoft.com>,
Takashi Iwai <tiwai@...e.com>,
"H. Peter Anvin" <hpa@...or.com>,
Bard Liao <yung-chuan.liao@...ux.intel.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Wei Liu <wei.liu@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>, x86@...nel.org,
kexec@...ts.infradead.org, alsa-devel@...a-project.org,
stable@...r.kernel.org, sound-open-firmware@...a-project.org,
linuxppc-dev@...ts.ozlabs.org, linux-hyperv@...r.kernel.org,
linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
xen-devel@...ts.xenproject.org
Subject: Re: [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@...nel.org> wrote:
>
> On Thu, Dec 1, 2022 at 12:08 PM Ricardo Ribalda <ribalda@...omium.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@...r.kernel.org
> > Fixes: 83bfc7e793b5 ("ASoC: SOF: core: unregister clients and machine drivers in .shutdown")
> > Signed-off-by: Ricardo Ribalda <ribalda@...omium.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
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