* [PATCH v2] drm: use trace_printk rather than printk in drm_dbg.
@ 2019-07-31 6:24 ` Fuqian Huang
0 siblings, 0 replies; 4+ messages in thread
From: Fuqian Huang @ 2019-07-31 6:24 UTC (permalink / raw)
Cc: Maarten Lankhorst, Maxime Ripard, Sean Paul, David Airlie,
Daniel Vetter, dri-devel, linux-kernel, Fuqian Huang
In drivers/gpu/drm/amd/amdgpu/amdgpu_ih.c,
amdgpu_ih_process calls DRM_DEBUG which calls drm_dbg and
finally calls printk.
As amdgpu_ih_process is called from an interrupt handler,
and interrupt handler should be short as possible.
As printk may lead to bogging down the system or can even
create a live lock. printk should not be used in IRQ context.
Instead, trace_printk is recommended in IRQ context.
Link: https://lwn.net/Articles/365835
Reviewed-by: Joe Perches <joe@perches.com>
Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
---
Changes in v2:
- Only make the interrupt uses the trace_printk to avoid
all 4000+ drm_dbg/DRM_DEBUG uses emitting a trace_printk.
drivers/gpu/drm/drm_print.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
index a17c8a14dba4..747835d16fa6 100644
--- a/drivers/gpu/drm/drm_print.c
+++ b/drivers/gpu/drm/drm_print.c
@@ -236,9 +236,13 @@ void drm_dbg(unsigned int category, const char *format, ...)
vaf.fmt = format;
vaf.va = &args;
- printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
- __builtin_return_address(0), &vaf);
-
+ if (in_interrupt()) {
+ trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
+ __builtin_return_address(0), &vaf);
+ } else {
+ printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
+ __builtin_return_address(0), &vaf);
+ }
va_end(args);
}
EXPORT_SYMBOL(drm_dbg);
--
2.11.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v2] drm: use trace_printk rather than printk in drm_dbg.
@ 2019-07-31 6:24 ` Fuqian Huang
0 siblings, 0 replies; 4+ messages in thread
From: Fuqian Huang @ 2019-07-31 6:24 UTC (permalink / raw)
Cc: Maarten Lankhorst, Maxime Ripard, Sean Paul, David Airlie,
Daniel Vetter, dri-devel, linux-kernel, Fuqian Huang
In drivers/gpu/drm/amd/amdgpu/amdgpu_ih.c,
amdgpu_ih_process calls DRM_DEBUG which calls drm_dbg and
finally calls printk.
As amdgpu_ih_process is called from an interrupt handler,
and interrupt handler should be short as possible.
As printk may lead to bogging down the system or can even
create a live lock. printk should not be used in IRQ context.
Instead, trace_printk is recommended in IRQ context.
Link: https://lwn.net/Articles/365835
Reviewed-by: Joe Perches <joe@perches.com>
Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
---
Changes in v2:
- Only make the interrupt uses the trace_printk to avoid
all 4000+ drm_dbg/DRM_DEBUG uses emitting a trace_printk.
drivers/gpu/drm/drm_print.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
index a17c8a14dba4..747835d16fa6 100644
--- a/drivers/gpu/drm/drm_print.c
+++ b/drivers/gpu/drm/drm_print.c
@@ -236,9 +236,13 @@ void drm_dbg(unsigned int category, const char *format, ...)
vaf.fmt = format;
vaf.va = &args;
- printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
- __builtin_return_address(0), &vaf);
-
+ if (in_interrupt()) {
+ trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
+ __builtin_return_address(0), &vaf);
+ } else {
+ printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
+ __builtin_return_address(0), &vaf);
+ }
va_end(args);
}
EXPORT_SYMBOL(drm_dbg);
--
2.11.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] drm: use trace_printk rather than printk in drm_dbg.
2019-07-31 6:24 ` Fuqian Huang
(?)
@ 2019-07-31 6:26 ` Joe Perches
2019-07-31 8:30 ` Daniel Vetter
-1 siblings, 1 reply; 4+ messages in thread
From: Joe Perches @ 2019-07-31 6:26 UTC (permalink / raw)
To: Fuqian Huang
Cc: Maarten Lankhorst, Maxime Ripard, Sean Paul, David Airlie,
Daniel Vetter, dri-devel, linux-kernel
On Wed, 2019-07-31 at 14:24 +0800, Fuqian Huang wrote:
> In drivers/gpu/drm/amd/amdgpu/amdgpu_ih.c,
> amdgpu_ih_process calls DRM_DEBUG which calls drm_dbg and
> finally calls printk.
> As amdgpu_ih_process is called from an interrupt handler,
> and interrupt handler should be short as possible.
>
> As printk may lead to bogging down the system or can even
> create a live lock. printk should not be used in IRQ context.
> Instead, trace_printk is recommended in IRQ context.
> Link: https://lwn.net/Articles/365835
>
> Reviewed-by: Joe Perches <joe@perches.com>
I made a suggestion. I did not review this.
Please do not add signatures like this if
not specifically given by someone.
> Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
> ---
> Changes in v2:
> - Only make the interrupt uses the trace_printk to avoid
> all 4000+ drm_dbg/DRM_DEBUG uses emitting a trace_printk.
>
> drivers/gpu/drm/drm_print.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
> index a17c8a14dba4..747835d16fa6 100644
> --- a/drivers/gpu/drm/drm_print.c
> +++ b/drivers/gpu/drm/drm_print.c
> @@ -236,9 +236,13 @@ void drm_dbg(unsigned int category, const char *format, ...)
> vaf.fmt = format;
> vaf.va = &args;
>
> - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> - __builtin_return_address(0), &vaf);
> -
> + if (in_interrupt()) {
> + trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> + __builtin_return_address(0), &vaf);
> + } else {
> + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> + __builtin_return_address(0), &vaf);
> + }
> va_end(args);
> }
> EXPORT_SYMBOL(drm_dbg);
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] drm: use trace_printk rather than printk in drm_dbg.
2019-07-31 6:26 ` Joe Perches
@ 2019-07-31 8:30 ` Daniel Vetter
0 siblings, 0 replies; 4+ messages in thread
From: Daniel Vetter @ 2019-07-31 8:30 UTC (permalink / raw)
To: Joe Perches
Cc: Fuqian Huang, Maarten Lankhorst, Maxime Ripard, Sean Paul,
David Airlie, Daniel Vetter, dri-devel, linux-kernel
On Tue, Jul 30, 2019 at 11:26:32PM -0700, Joe Perches wrote:
> On Wed, 2019-07-31 at 14:24 +0800, Fuqian Huang wrote:
> > In drivers/gpu/drm/amd/amdgpu/amdgpu_ih.c,
> > amdgpu_ih_process calls DRM_DEBUG which calls drm_dbg and
> > finally calls printk.
> > As amdgpu_ih_process is called from an interrupt handler,
> > and interrupt handler should be short as possible.
> >
> > As printk may lead to bogging down the system or can even
> > create a live lock. printk should not be used in IRQ context.
> > Instead, trace_printk is recommended in IRQ context.
> > Link: https://lwn.net/Articles/365835
> >
> > Reviewed-by: Joe Perches <joe@perches.com>
>
> I made a suggestion. I did not review this.
>
> Please do not add signatures like this if
> not specifically given by someone.
+1
> > Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
> > ---
> > Changes in v2:
> > - Only make the interrupt uses the trace_printk to avoid
> > all 4000+ drm_dbg/DRM_DEBUG uses emitting a trace_printk.
> >
> > drivers/gpu/drm/drm_print.c | 10 +++++++---
> > 1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
> > index a17c8a14dba4..747835d16fa6 100644
> > --- a/drivers/gpu/drm/drm_print.c
> > +++ b/drivers/gpu/drm/drm_print.c
> > @@ -236,9 +236,13 @@ void drm_dbg(unsigned int category, const char *format, ...)
Right above here is a check for drm_debug, which defaults to off, so in
production this all has 0 impact. But changing all the debug output from
dmesg to tracing is sure to break everyone's CI and test setups.
I'm all for cleaning up the drm logging stuff (it's a real mess), but it's
a very delicate house of cards and with thousands of users, not easy to
change. Unfortunately I don't really have a solid recommendation for what
the ideal drm logging should look like. Plus we already have a pile of
competing approaches ...
-Daniel
> > vaf.fmt = format;
> > vaf.va = &args;
> >
> > - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > - __builtin_return_address(0), &vaf);
> > -
> > + if (in_interrupt()) {
> > + trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > + __builtin_return_address(0), &vaf);
> > + } else {
> > + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > + __builtin_return_address(0), &vaf);
> > + }
> > va_end(args);
> > }
> > EXPORT_SYMBOL(drm_dbg);
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-07-31 8:30 UTC | newest]
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2019-07-31 6:24 [PATCH v2] drm: use trace_printk rather than printk in drm_dbg Fuqian Huang
2019-07-31 6:24 ` Fuqian Huang
2019-07-31 6:26 ` Joe Perches
2019-07-31 8:30 ` Daniel Vetter
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