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SubjectRe: [PATCH v2] drm: use trace_printk rather than printk in drm_dbg.
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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);

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