[PATCH 0/4] lib/vsprintf: Remove atomic-unsafe support for printk format %pCr

[PATCH 0/4] lib/vsprintf: Remove atomic-unsafe support for printk format %pCr

[Geert Uytterhoeven]

	Hi all,

"%pCr" formats the current rate of a clock, and calls clk_get_rate().
The latter obtains a mutex, hence it must not be called from atomic
context.  As vsprintf() (and e.g. printk()) must be callable from any
context, it's better to remove support for this (rarely-used) format.

This patch series:
  - Changes all existing users of "%pCr" to print the result of
    clk_get_rate() directly, which is safe as they all do this in task
    context only,
  - Removes support for the "%pCr" printk format.

Note that any remaining out-of-tree users will start seeing the clock's
name printed instead of its rate.

Thanks for your comments!

Geert Uytterhoeven (4):
  clk: renesas: cpg-mssr: Stop using printk format %pCr
  thermal: bcm2835: Stop using printk format %pCr
  serial: sh-sci: Stop using printk format %pCr
  lib/vsprintf: Remove atomic-unsafe support for %pCr

 Documentation/core-api/printk-formats.rst  | 3 +--
 drivers/clk/renesas/renesas-cpg-mssr.c     | 9 +++++----
 drivers/thermal/broadcom/bcm2835_thermal.c | 4 ++--
 drivers/tty/serial/sh-sci.c                | 4 ++--
 lib/vsprintf.c                             | 3 ---
 5 files changed, 10 insertions(+), 13 deletions(-)

-- 
2.7.4

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

[PATCH 1/4] clk: renesas: cpg-mssr: Stop using printk format %pCr

[Geert Uytterhoeven]

Printk format "%pCr" will be removed soon, as clk_get_rate() must not be
called in atomic context.

Replace it by open-coding the operation.  This is safe here, as the code
runs in task context.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/clk/renesas/renesas-cpg-mssr.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/renesas/renesas-cpg-mssr.c b/drivers/clk/renesas/renesas-cpg-mssr.c
index 49e510691eeeab07..f4b013e9352d9efc 100644
--- a/drivers/clk/renesas/renesas-cpg-mssr.c
+++ b/drivers/clk/renesas/renesas-cpg-mssr.c
@@ -258,8 +258,9 @@ struct clk *cpg_mssr_clk_src_twocell_get(struct of_phandle_args *clkspec,
 		dev_err(dev, "Cannot get %s clock %u: %ld", type, clkidx,
 		       PTR_ERR(clk));
 	else
-		dev_dbg(dev, "clock (%u, %u) is %pC at %pCr Hz\n",
-			clkspec->args[0], clkspec->args[1], clk, clk);
+		dev_dbg(dev, "clock (%u, %u) is %pC at %lu Hz\n",
+			clkspec->args[0], clkspec->args[1], clk,
+			clk_get_rate(clk));
 	return clk;
 }
 
@@ -326,7 +327,7 @@ static void __init cpg_mssr_register_core_clk(const struct cpg_core_clk *core,
 	if (IS_ERR_OR_NULL(clk))
 		goto fail;
 
-	dev_dbg(dev, "Core clock %pC at %pCr Hz\n", clk, clk);
+	dev_dbg(dev, "Core clock %pC at %lu Hz\n", clk, clk_get_rate(clk));
 	priv->clks[id] = clk;
 	return;
 
@@ -392,7 +393,7 @@ static void __init cpg_mssr_register_mod_clk(const struct mssr_mod_clk *mod,
 	if (IS_ERR(clk))
 		goto fail;
 
-	dev_dbg(dev, "Module clock %pC at %pCr Hz\n", clk, clk);
+	dev_dbg(dev, "Module clock %pC at %lu Hz\n", clk, clk_get_rate(clk));
 	priv->clks[id] = clk;
 	priv->smstpcr_saved[clock->index / 32].mask |= BIT(clock->index % 32);
 	return;
-- 
2.7.4

[PATCH 2/4] thermal: bcm2835: Stop using printk format %pCr

[Geert Uytterhoeven]

Printk format "%pCr" will be removed soon, as clk_get_rate() must not be
called in atomic context.

Replace it by printing the variable that already holds the clock rate.
Note that calling clk_get_rate() is safe here, as the code runs in task
context.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/thermal/broadcom/bcm2835_thermal.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/broadcom/bcm2835_thermal.c b/drivers/thermal/broadcom/bcm2835_thermal.c
index a4d6a0e2e9938190..23ad4f9f21438e45 100644
--- a/drivers/thermal/broadcom/bcm2835_thermal.c
+++ b/drivers/thermal/broadcom/bcm2835_thermal.c
@@ -213,8 +213,8 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
 	rate = clk_get_rate(data->clk);
 	if ((rate < 1920000) || (rate > 5000000))
 		dev_warn(&pdev->dev,
-			 "Clock %pCn running at %pCr Hz is outside of the recommended range: 1.92 to 5MHz\n",
-			 data->clk, data->clk);
+			 "Clock %pCn running at %lu Hz is outside of the recommended range: 1.92 to 5MHz\n",
+			 data->clk, rate);
 
 	/* register of thermal sensor and get info from DT */
 	tz = thermal_zone_of_sensor_register(&pdev->dev, 0, data,
-- 
2.7.4

[PATCH 3/4] serial: sh-sci: Stop using printk format %pCr

[Geert Uytterhoeven]

Printk format "%pCr" will be removed soon, as clk_get_rate() must not be
called in atomic context.

Replace it by open-coding the operation.  This is safe here, as the code
runs in task context.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/tty/serial/sh-sci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index b46b146524ce7495..c181eb37f98509e6 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -2724,8 +2724,8 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
 			dev_dbg(dev, "failed to get %s (%ld)\n", clk_names[i],
 				PTR_ERR(clk));
 		else
-			dev_dbg(dev, "clk %s is %pC rate %pCr\n", clk_names[i],
-				clk, clk);
+			dev_dbg(dev, "clk %s is %pC rate %lu\n", clk_names[i],
+				clk, clk_get_rate(clk));
 		sci_port->clks[i] = IS_ERR(clk) ? NULL : clk;
 	}
 	return 0;
-- 
2.7.4

[PATCH 4/4] lib/vsprintf: Remove atomic-unsafe support for %pCr

[Geert Uytterhoeven]

"%pCr" formats the current rate of a clock, and calls clk_get_rate().
The latter obtains a mutex, hence it must not be called from atomic
context.

Remove support for this rarely-used format, as vsprintf() (and e.g.
printk()) must be callable from any context.

Any remaining out-of-tree users will start seeing the clock's name
printed instead of its rate.

Reported-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Fixes: 900cca2944254edd ("lib/vsprintf: add %pC{,n,r} format specifiers for clocks")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 Documentation/core-api/printk-formats.rst | 3 +--
 lib/vsprintf.c                            | 3 ---
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index eb30efdd2e789616..25dc591cb1108790 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -419,11 +419,10 @@ struct clk
 
 	%pC	pll1
 	%pCn	pll1
-	%pCr	1560000000
 
 For printing struct clk structures. %pC and %pCn print the name
 (Common Clock Framework) or address (legacy clock framework) of the
-structure; %pCr prints the current clock rate.
+structure.
 
 Passed by reference.
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 247a7e0bf24f6f74..a48aaa79d352313a 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1469,9 +1469,6 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
 		return string(buf, end, NULL, spec);
 
 	switch (fmt[1]) {
-	case 'r':
-		return number(buf, end, clk_get_rate(clk), spec);
-
 	case 'n':
 	default:
 #ifdef CONFIG_COMMON_CLK
-- 
2.7.4

Re: [PATCH 2/4] thermal: bcm2835: Stop using printk format %pCr

[Stefan Wahren]

Am 01.06.2018 um 11:28 schrieb Geert Uytterhoeven:
> Printk format "%pCr" will be removed soon, as clk_get_rate() must not be
> called in atomic context.
>
> Replace it by printing the variable that already holds the clock rate.
> Note that calling clk_get_rate() is safe here, as the code runs in task
> context.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>

Thanks

Re: [PATCH 0/4] lib/vsprintf: Remove atomic-unsafe support for printk format %pCr

[Linus Torvalds]

On Fri, Jun 1, 2018 at 4:29 AM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
>
> This patch series:
>   - Changes all existing users of "%pCr" to print the result of
>     clk_get_rate() directly, which is safe as they all do this in task
>     context only,
>   - Removes support for the "%pCr" printk format.

Looks good to me.

What tree will this go through? The normal printk one? Just checking
that this doesn't end up falling through the cracks because nobody
knows who would take it...

               Linus

Re: [PATCH 0/4] lib/vsprintf: Remove atomic-unsafe support for printk format %pCr

[Andy Shevchenko]

On Fri, Jun 1, 2018 at 2:00 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Fri, Jun 1, 2018 at 4:29 AM Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
>>
>> This patch series:
>>   - Changes all existing users of "%pCr" to print the result of
>>     clk_get_rate() directly, which is safe as they all do this in task
>>     context only,
>>   - Removes support for the "%pCr" printk format.
>
> Looks good to me.
>
> What tree will this go through? The normal printk one? Just checking
> that this doesn't end up falling through the cracks because nobody
> knows who would take it...

We discussed few month before with Petr that he would take care of the
patches against vsprintf.c.
I think this is the case here.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 0/4] lib/vsprintf: Remove atomic-unsafe support for printk format %pCr

[Petr Mladek]

On Fri 2018-06-01 06:00:47, Linus Torvalds wrote:
> On Fri, Jun 1, 2018 at 4:29 AM Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> >
> > This patch series:
> >   - Changes all existing users of "%pCr" to print the result of
> >     clk_get_rate() directly, which is safe as they all do this in task
> >     context only,
> >   - Removes support for the "%pCr" printk format.
> 
> Looks good to me.
> 
> What tree will this go through? The normal printk one? Just checking
> that this doesn't end up falling through the cracks because nobody
> knows who would take it...

I will take it via printk.git. There already is bunch of vsprintf
changes for-4.18.

Best Regards,
Petr

Re: [PATCH 0/4] lib/vsprintf: Remove atomic-unsafe support for printk format %pCr

[Petr Mladek]

On Fri 2018-06-01 13:47:38, Petr Mladek wrote:
> On Fri 2018-06-01 06:00:47, Linus Torvalds wrote:
> > On Fri, Jun 1, 2018 at 4:29 AM Geert Uytterhoeven
> > <geert+renesas@glider.be> wrote:
> > >
> > > This patch series:
> > >   - Changes all existing users of "%pCr" to print the result of
> > >     clk_get_rate() directly, which is safe as they all do this in task
> > >     context only,
> > >   - Removes support for the "%pCr" printk format.
> > 
> > Looks good to me.
> > 
> > What tree will this go through? The normal printk one? Just checking
> > that this doesn't end up falling through the cracks because nobody
> > knows who would take it...
> 
> I will take it via printk.git. There already is bunch of vsprintf
> changes for-4.18.

It is in printk.git, branch for-4.18-vsprintf-pcr-removal now.

Also I have added Cc: stable@vger.kernel.org into the commit messages.

Best Regards,
Petr

Re: [PATCH 0/4] lib/vsprintf: Remove atomic-unsafe support for printk format %pCr

[Geert Uytterhoeven]

Hi Petr,

On Fri, Jun 1, 2018 at 5:19 PM, Petr Mladek <pmladek@suse.com> wrote:
> On Fri 2018-06-01 13:47:38, Petr Mladek wrote:
>> On Fri 2018-06-01 06:00:47, Linus Torvalds wrote:
>> > On Fri, Jun 1, 2018 at 4:29 AM Geert Uytterhoeven
>> > <geert+renesas@glider.be> wrote:
>> > >
>> > > This patch series:
>> > >   - Changes all existing users of "%pCr" to print the result of
>> > >     clk_get_rate() directly, which is safe as they all do this in task
>> > >     context only,
>> > >   - Removes support for the "%pCr" printk format.
>> >
>> > Looks good to me.
>> >
>> > What tree will this go through? The normal printk one? Just checking
>> > that this doesn't end up falling through the cracks because nobody
>> > knows who would take it...
>>
>> I will take it via printk.git. There already is bunch of vsprintf
>> changes for-4.18.
>
> It is in printk.git, branch for-4.18-vsprintf-pcr-removal now.

Thank you.

> Also I have added Cc: stable@vger.kernel.org into the commit messages.

I can confirm all stable version references ("v4.x+") match.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 1/4] clk: renesas: cpg-mssr: Stop using printk format %pCr

[Stephen Boyd]

Quoting Geert Uytterhoeven (2018-06-01 02:28:19)
> Printk format "%pCr" will be removed soon, as clk_get_rate() must not be
> called in atomic context.
> =

> Replace it by open-coding the operation.  This is safe here, as the code
> runs in task context.
> =

> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---

Acked-by: Stephen Boyd <sboyd@kernel.org>