[PATCH] doc: refer to kdump in oops-tracing.txt

Kdump has been merged and supported on several architectures. It is better
to encourage to use kdump rather than non standard kernel crash dump
patches.

Signed-off-by: Akinobu Mita <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/oops-tracing.txt

···
     run a null modem to a second machine and capture the output there
     using your favourite communication program.  Minicom works well.
 
-(3) Patch the kernel with one of the crash dump patches.  These save
-    data to a floppy disk or video rom or a swap partition.  None of
-    these are standard kernel patches so you have to find and apply
-    them yourself.  Search kernel archives for kmsgdump, lkcd and
-    oops+smram.
+(3) Use Kdump (see Documentation/kdump/kdump.txt),
+    extract the kernel ring buffer from old memory with using dmesg
+    gdbmacro in Documentation/kdump/gdbmacros.txt.
 
 
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