* [PATCH] drm: use trace_printk rather than printk in drm_dbg.
@ 2019-07-31 2:45 Fuqian Huang
2019-07-31 6:06 ` Joe Perches
0 siblings, 1 reply; 3+ messages in thread
From: Fuqian Huang @ 2019-07-31 2:45 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.
Link: https://lwn.net/Articles/365835
Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
---
drivers/gpu/drm/drm_print.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
index a17c8a14dba4..90cded140146 100644
--- a/drivers/gpu/drm/drm_print.c
+++ b/drivers/gpu/drm/drm_print.c
@@ -236,7 +236,7 @@ void drm_dbg(unsigned int category, const char *format, ...)
vaf.fmt = format;
vaf.va = &args;
- printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
+ trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
__builtin_return_address(0), &vaf);
va_end(args);
--
2.11.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] drm: use trace_printk rather than printk in drm_dbg.
2019-07-31 2:45 [PATCH] drm: use trace_printk rather than printk in drm_dbg Fuqian Huang
@ 2019-07-31 6:06 ` Joe Perches
2019-07-31 6:26 ` Fuqian Huang
0 siblings, 1 reply; 3+ messages in thread
From: Joe Perches @ 2019-07-31 6:06 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 10:45 +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.
> Link: https://lwn.net/Articles/365835
[]
> diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
[]
> @@ -236,7 +236,7 @@ void drm_dbg(unsigned int category, const char *format, ...)
> vaf.fmt = format;
> vaf.va = &args;
>
> - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> + trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> __builtin_return_address(0), &vaf);
>
> va_end(args);
This makes all 4000+ drm_dbg/DRM_DEBUG uses emit
a trace_printk.
I suggest instead you make only the interrupt uses
use a different function and not drm_dbg.
Or maybe add an in_interrupt() check like
if (in_interrupt())
printk(KERN_DEBUG etc...)
else
trace_printk(etc...)
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] drm: use trace_printk rather than printk in drm_dbg.
2019-07-31 6:06 ` Joe Perches
@ 2019-07-31 6:26 ` Fuqian Huang
0 siblings, 0 replies; 3+ messages in thread
From: Fuqian Huang @ 2019-07-31 6:26 UTC (permalink / raw)
To: Joe Perches
Cc: Maarten Lankhorst, Maxime Ripard, Sean Paul, David Airlie,
Daniel Vetter, dri-devel, Linux Kernel Mailing List
Joe Perches <joe@perches.com> 於 2019年7月31日週三 下午2:06寫道:
>
> On Wed, 2019-07-31 at 10:45 +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.
> > Link: https://lwn.net/Articles/365835
> []
> > diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
> []
> > @@ -236,7 +236,7 @@ void drm_dbg(unsigned int category, const char *format, ...)
> > vaf.fmt = format;
> > vaf.va = &args;
> >
> > - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > + trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > __builtin_return_address(0), &vaf);
> >
> > va_end(args);
>
> This makes all 4000+ drm_dbg/DRM_DEBUG uses emit
> a trace_printk.
>
> I suggest instead you make only the interrupt uses
> use a different function and not drm_dbg.
>
> Or maybe add an in_interrupt() check like
>
> if (in_interrupt())
> printk(KERN_DEBUG etc...)
> else
> trace_printk(etc...)
I will send a v2 patch to fix this.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-07-31 2:45 [PATCH] drm: use trace_printk rather than printk in drm_dbg Fuqian Huang
2019-07-31 6:06 ` Joe Perches
2019-07-31 6:26 ` Fuqian Huang
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