[PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[Dangyi Liu]

logged_chars would be set to 0 by `dmesg -c`, but full dmesg is useful
for debugging. So instead of using logged_chars directly, we calculate
it by ourselves.

Now logged_chars is set to the minimum of log_end and log_buf_len, as
the same logic as crash utility is using.

Signed-off-by: Dangyi Liu <dliu@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
---
Changes:
  v1->v2: Update comment and commit message.
  v2->v3: Adjust maximum line length

 vmcore-dmesg/vmcore-dmesg.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
index f47ee11..0364636 100644
--- a/vmcore-dmesg/vmcore-dmesg.c
+++ b/vmcore-dmesg/vmcore-dmesg.c
@@ -540,6 +540,12 @@ static void dump_dmesg_legacy(int fd)
 		exit(53);
 	}
 
+	/*
+	 * To collect full dmesg including the part before `dmesg -c` is useful
+	 * for later debugging. Use same logic as what crash utility is using.
+	 */
+	logged_chars = log_end < log_buf_len ? log_end : log_buf_len;
+
 	write_to_stdout(buf + (log_buf_len -  logged_chars), logged_chars);
 }
 
-- 
2.4.3


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Re: [PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[Dave Young]

On 10/28/15 at 05:15pm, Dangyi Liu wrote:
> logged_chars would be set to 0 by `dmesg -c`, but full dmesg is useful
> for debugging. So instead of using logged_chars directly, we calculate
> it by ourselves.
> 
> Now logged_chars is set to the minimum of log_end and log_buf_len, as
> the same logic as crash utility is using.
> 
> Signed-off-by: Dangyi Liu <dliu@redhat.com>
> Cc: Dave Young <dyoung@redhat.com>
> ---
> Changes:
>   v1->v2: Update comment and commit message.
>   v2->v3: Adjust maximum line length
> 
>  vmcore-dmesg/vmcore-dmesg.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
> index f47ee11..0364636 100644
> --- a/vmcore-dmesg/vmcore-dmesg.c
> +++ b/vmcore-dmesg/vmcore-dmesg.c
> @@ -540,6 +540,12 @@ static void dump_dmesg_legacy(int fd)
>  		exit(53);
>  	}
>  
> +	/*
> +	 * To collect full dmesg including the part before `dmesg -c` is useful
> +	 * for later debugging. Use same logic as what crash utility is using.
> +	 */
> +	logged_chars = log_end < log_buf_len ? log_end : log_buf_len;
> +
>  	write_to_stdout(buf + (log_buf_len -  logged_chars), logged_chars);
>  }
>  
> -- 
> 2.4.3
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
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Acked-by: Dave Young <dyoung@redhat.com>

Thanks
Dave

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Re: [PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[Dangyi Liu]

Simon,

Could you help to review this patch?

Thanks,
Dangyi Liu

On Wed, 2015-10-28 at 17:15 +0800, Dangyi Liu wrote:
> logged_chars would be set to 0 by `dmesg -c`, but full dmesg is
> useful
> for debugging. So instead of using logged_chars directly, we
> calculate
> it by ourselves.
> 
> Now logged_chars is set to the minimum of log_end and log_buf_len, as
> the same logic as crash utility is using.
> 
> Signed-off-by: Dangyi Liu <dliu@redhat.com>
> Cc: Dave Young <dyoung@redhat.com>
> ---
> Changes:
>   v1->v2: Update comment and commit message.
>   v2->v3: Adjust maximum line length
> 
>  vmcore-dmesg/vmcore-dmesg.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-
> dmesg.c
> index f47ee11..0364636 100644
> --- a/vmcore-dmesg/vmcore-dmesg.c
> +++ b/vmcore-dmesg/vmcore-dmesg.c
> @@ -540,6 +540,12 @@ static void dump_dmesg_legacy(int fd)
>  		exit(53);
>  	}
>  
> +	/*
> +	 * To collect full dmesg including the part before `dmesg
> -c` is useful
> +	 * for later debugging. Use same logic as what crash utility
> is using.
> +	 */
> +	logged_chars = log_end < log_buf_len ? log_end :
> log_buf_len;
> +
>  	write_to_stdout(buf + (log_buf_len -  logged_chars),
> logged_chars);
>  }
>  

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Re: [PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[Dave Young]

On 11/18/15 at 01:24pm, Dangyi Liu wrote:
> Simon,
> 
> Could you help to review this patch?
> 
> Thanks,
> Dangyi Liu
> 
> On Wed, 2015-10-28 at 17:15 +0800, Dangyi Liu wrote:
> > logged_chars would be set to 0 by `dmesg -c`, but full dmesg is
> > useful
> > for debugging. So instead of using logged_chars directly, we
> > calculate
> > it by ourselves.
> > 
> > Now logged_chars is set to the minimum of log_end and log_buf_len, as
> > the same logic as crash utility is using.
> > 
> > Signed-off-by: Dangyi Liu <dliu@redhat.com>
> > Cc: Dave Young <dyoung@redhat.com>
> > ---
> > Changes:
> >   v1->v2: Update comment and commit message.
> >   v2->v3: Adjust maximum line length
> > 
> >  vmcore-dmesg/vmcore-dmesg.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-
> > dmesg.c
> > index f47ee11..0364636 100644
> > --- a/vmcore-dmesg/vmcore-dmesg.c
> > +++ b/vmcore-dmesg/vmcore-dmesg.c
> > @@ -540,6 +540,12 @@ static void dump_dmesg_legacy(int fd)
> >  		exit(53);
> >  	}
> >  
> > +	/*
> > +	 * To collect full dmesg including the part before `dmesg
> > -c` is useful
> > +	 * for later debugging. Use same logic as what crash utility
> > is using.
> > +	 */
> > +	logged_chars = log_end < log_buf_len ? log_end :
> > log_buf_len;
> > +
> >  	write_to_stdout(buf + (log_buf_len -  logged_chars),
> > logged_chars);
> >  }
> >  
> 

Simon,

What's your opinion about this patch? It is a rh internal report.
Current code make sense, adding the patch will be slight better though
for kdump case. But if you do not like it we can ignore it and close
the bug.

Thanks
Dave

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Re: [PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[Simon Horman]

On Tue, Dec 08, 2015 at 11:36:04AM +0800, Dave Young wrote:
> On 11/18/15 at 01:24pm, Dangyi Liu wrote:
> > Simon,
> > 
> > Could you help to review this patch?
> > 
> > Thanks,
> > Dangyi Liu
> > 
> > On Wed, 2015-10-28 at 17:15 +0800, Dangyi Liu wrote:
> > > logged_chars would be set to 0 by `dmesg -c`, but full dmesg is
> > > useful
> > > for debugging. So instead of using logged_chars directly, we
> > > calculate
> > > it by ourselves.
> > > 
> > > Now logged_chars is set to the minimum of log_end and log_buf_len, as
> > > the same logic as crash utility is using.
> > > 
> > > Signed-off-by: Dangyi Liu <dliu@redhat.com>
> > > Cc: Dave Young <dyoung@redhat.com>
> > > ---
> > > Changes:
> > >   v1->v2: Update comment and commit message.
> > >   v2->v3: Adjust maximum line length
> > > 
> > >  vmcore-dmesg/vmcore-dmesg.c | 6 ++++++
> > >  1 file changed, 6 insertions(+)
> > > 
> > > diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-
> > > dmesg.c
> > > index f47ee11..0364636 100644
> > > --- a/vmcore-dmesg/vmcore-dmesg.c
> > > +++ b/vmcore-dmesg/vmcore-dmesg.c
> > > @@ -540,6 +540,12 @@ static void dump_dmesg_legacy(int fd)
> > >  		exit(53);
> > >  	}
> > >  
> > > +	/*
> > > +	 * To collect full dmesg including the part before `dmesg
> > > -c` is useful
> > > +	 * for later debugging. Use same logic as what crash utility
> > > is using.
> > > +	 */
> > > +	logged_chars = log_end < log_buf_len ? log_end :
> > > log_buf_len;
> > > +
> > >  	write_to_stdout(buf + (log_buf_len -  logged_chars),
> > > logged_chars);
> > >  }
> > >  
> > 
> 
> Simon,
> 
> What's your opinion about this patch? It is a rh internal report.
> Current code make sense, adding the patch will be slight better though
> for kdump case. But if you do not like it we can ignore it and close
> the bug.

This seems reasonable to me, but perhaps the logic should only kick
in if logged_chars is 0?

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Re: [PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[Dave Young]

On 12/08/15 at 03:04pm, Simon Horman wrote:
> On Tue, Dec 08, 2015 at 11:36:04AM +0800, Dave Young wrote:
> > On 11/18/15 at 01:24pm, Dangyi Liu wrote:
> > > Simon,
> > > 
> > > Could you help to review this patch?
> > > 
> > > Thanks,
> > > Dangyi Liu
> > > 
> > > On Wed, 2015-10-28 at 17:15 +0800, Dangyi Liu wrote:
> > > > logged_chars would be set to 0 by `dmesg -c`, but full dmesg is
> > > > useful
> > > > for debugging. So instead of using logged_chars directly, we
> > > > calculate
> > > > it by ourselves.
> > > > 
> > > > Now logged_chars is set to the minimum of log_end and log_buf_len, as
> > > > the same logic as crash utility is using.
> > > > 
> > > > Signed-off-by: Dangyi Liu <dliu@redhat.com>
> > > > Cc: Dave Young <dyoung@redhat.com>
> > > > ---
> > > > Changes:
> > > >   v1->v2: Update comment and commit message.
> > > >   v2->v3: Adjust maximum line length
> > > > 
> > > >  vmcore-dmesg/vmcore-dmesg.c | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > > 
> > > > diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-
> > > > dmesg.c
> > > > index f47ee11..0364636 100644
> > > > --- a/vmcore-dmesg/vmcore-dmesg.c
> > > > +++ b/vmcore-dmesg/vmcore-dmesg.c
> > > > @@ -540,6 +540,12 @@ static void dump_dmesg_legacy(int fd)
> > > >  		exit(53);
> > > >  	}
> > > >  
> > > > +	/*
> > > > +	 * To collect full dmesg including the part before `dmesg
> > > > -c` is useful
> > > > +	 * for later debugging. Use same logic as what crash utility
> > > > is using.
> > > > +	 */
> > > > +	logged_chars = log_end < log_buf_len ? log_end :
> > > > log_buf_len;
> > > > +
> > > >  	write_to_stdout(buf + (log_buf_len -  logged_chars),
> > > > logged_chars);
> > > >  }
> > > >  
> > > 
> > 
> > Simon,
> > 
> > What's your opinion about this patch? It is a rh internal report.
> > Current code make sense, adding the patch will be slight better though
> > for kdump case. But if you do not like it we can ignore it and close
> > the bug.
> 
> This seems reasonable to me, but perhaps the logic should only kick
> in if logged_chars is 0?
> 

It will contain at least panic messages to it is unlikely logged_chars = 0?

Thanks
Dave

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Re: [PATCH v3] vmcore-dmesg: Collect full dmesg regardless of logged_chars

[Simon Horman]

On Wed, Dec 09, 2015 at 10:28:03AM +0800, Dave Young wrote:
> On 12/08/15 at 03:04pm, Simon Horman wrote:
> > On Tue, Dec 08, 2015 at 11:36:04AM +0800, Dave Young wrote:
> > > On 11/18/15 at 01:24pm, Dangyi Liu wrote:
> > > > Simon,
> > > > 
> > > > Could you help to review this patch?
> > > > 
> > > > Thanks,
> > > > Dangyi Liu
> > > > 
> > > > On Wed, 2015-10-28 at 17:15 +0800, Dangyi Liu wrote:
> > > > > logged_chars would be set to 0 by `dmesg -c`, but full dmesg is
> > > > > useful
> > > > > for debugging. So instead of using logged_chars directly, we
> > > > > calculate
> > > > > it by ourselves.
> > > > > 
> > > > > Now logged_chars is set to the minimum of log_end and log_buf_len, as
> > > > > the same logic as crash utility is using.
> > > > > 
> > > > > Signed-off-by: Dangyi Liu <dliu@redhat.com>
> > > > > Cc: Dave Young <dyoung@redhat.com>
> > > > > ---
> > > > > Changes:
> > > > >   v1->v2: Update comment and commit message.
> > > > >   v2->v3: Adjust maximum line length
> > > > > 
> > > > >  vmcore-dmesg/vmcore-dmesg.c | 6 ++++++
> > > > >  1 file changed, 6 insertions(+)
> > > > > 
> > > > > diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-
> > > > > dmesg.c
> > > > > index f47ee11..0364636 100644
> > > > > --- a/vmcore-dmesg/vmcore-dmesg.c
> > > > > +++ b/vmcore-dmesg/vmcore-dmesg.c
> > > > > @@ -540,6 +540,12 @@ static void dump_dmesg_legacy(int fd)
> > > > >  		exit(53);
> > > > >  	}
> > > > >  
> > > > > +	/*
> > > > > +	 * To collect full dmesg including the part before `dmesg
> > > > > -c` is useful
> > > > > +	 * for later debugging. Use same logic as what crash utility
> > > > > is using.
> > > > > +	 */
> > > > > +	logged_chars = log_end < log_buf_len ? log_end :
> > > > > log_buf_len;
> > > > > +
> > > > >  	write_to_stdout(buf + (log_buf_len -  logged_chars),
> > > > > logged_chars);
> > > > >  }
> > > > >  
> > > > 
> > > 
> > > Simon,
> > > 
> > > What's your opinion about this patch? It is a rh internal report.
> > > Current code make sense, adding the patch will be slight better though
> > > for kdump case. But if you do not like it we can ignore it and close
> > > the bug.
> > 
> > This seems reasonable to me, but perhaps the logic should only kick
> > in if logged_chars is 0?
> > 
> 
> It will contain at least panic messages to it is unlikely logged_chars = 0?

Understood. I have applied the patch.

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