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| author | Ingo Molnar <mingo@elte.hu> | 2010-11-18 13:22:14 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2010-11-18 13:22:26 +0100 |
| commit | 92fd4d4d67b945c0766416284d4ab236b31542c4 (patch) | |
| tree | 00b8b5f90748f752ccaba3dddbe271091d93543a /Documentation/dynamic-debug-howto.txt | |
| parent | sched: Make sched_param argument static in sched_setscheduler() callers (diff) | |
| parent | Linux 2.6.37-rc2 (diff) | |
| download | linux-92fd4d4d67b945c0766416284d4ab236b31542c4.tar.xz linux-92fd4d4d67b945c0766416284d4ab236b31542c4.zip | |
Merge commit 'v2.6.37-rc2' into sched/core
Merge reason: Move to a .37-rc base.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/dynamic-debug-howto.txt')
| -rw-r--r-- | Documentation/dynamic-debug-howto.txt | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/Documentation/dynamic-debug-howto.txt b/Documentation/dynamic-debug-howto.txt index 674c5663d346..58ea64a96165 100644 --- a/Documentation/dynamic-debug-howto.txt +++ b/Documentation/dynamic-debug-howto.txt @@ -24,7 +24,7 @@ Dynamic debug has even more useful features: read to display the complete list of known debug statements, to help guide you Controlling dynamic debug Behaviour -=============================== +=================================== The behaviour of pr_debug()/dev_debug()s are controlled via writing to a control file in the 'debugfs' filesystem. Thus, you must first mount the debugfs @@ -212,6 +212,26 @@ Note the regexp ^[-+=][scp]+$ matches a flags specification. Note also that there is no convenient syntax to remove all the flags at once, you need to use "-psc". + +Debug messages during boot process +================================== + +To be able to activate debug messages during the boot process, +even before userspace and debugfs exists, use the boot parameter: +ddebug_query="QUERY" + +QUERY follows the syntax described above, but must not exceed 1023 +characters. The enablement of debug messages is done as an arch_initcall. +Thus you can enable debug messages in all code processed after this +arch_initcall via this boot parameter. +On an x86 system for example ACPI enablement is a subsys_initcall and +ddebug_query="file ec.c +p" +will show early Embedded Controller transactions during ACPI setup if +your machine (typically a laptop) has an Embedded Controller. +PCI (or other devices) initialization also is a hot candidate for using +this boot parameter for debugging purposes. + + Examples ======== |