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[Bug translator/19396] systemtap can't find certain kernel tracepoints
- From: "dsmith at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sourceware dot org
- Date: Wed, 06 Jan 2016 17:12:51 +0000
- Subject: [Bug translator/19396] systemtap can't find certain kernel tracepoints
- Auto-submitted: auto-generated
- References: <bug-19396-6586 at http dot sourceware dot org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=19396
--- Comment #1 from David Smith <dsmith at redhat dot com> ---
I'm seeing something wacky here. This is on 2.6.32-573.el6.ppc64:
====
# stap --poison-cache -L 'kernel.trace("*module*")'
kernel.trace("jbd:module_free") $mod:struct module*
kernel.trace("jbd:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("jbd:module_load") $mod:struct module*
kernel.trace("jbd:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("jbd:module_request") $name:char* $wait:bool $ip:long unsigned int
====
So, when '--poison-cache' is used, for some reason stap thinks the module_*
tracepoints are in the "jbd" subsystem instead of in the "module" subsystem.
But, you can list them as being in the "module" subsystem:
====
# stap -L 'kernel.trace("*module*")'
kernel.trace("module:module_free") $mod:struct module*
kernel.trace("module:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("module:module_load") $mod:struct module*
kernel.trace("module:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("module:module_request") $name:char* $wait:bool $ip:long unsigned
int
====
You can actually see them in either subsystem:
====
# stap -L 'kernel.trace("jbd:module*")'
kernel.trace("jbd:module_free") $mod:struct module*
kernel.trace("jbd:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("jbd:module_load") $mod:struct module*
kernel.trace("jbd:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("jbd:module_request") $name:char* $wait:bool $ip:long unsigned int
# stap -L 'kernel.trace("module:module*")'
kernel.trace("module:module_free") $mod:struct module*
kernel.trace("module:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("module:module_load") $mod:struct module*
kernel.trace("module:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("module:module_request") $name:char* $wait:bool $ip:long unsigned
int
====
Note that if you try this with a completely non-existing subsystem, you do get
the correct result (of nothing):
====
# stap -L 'kernel.trace("foo:module*")'
#
====
It looks like you can look up the module tracepoints in about any (existing)
subsystem:
====
# stap -L 'kernel.trace("ext4:module*")'
kernel.trace("ext4:module_free") $mod:struct module*
kernel.trace("ext4:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("ext4:module_load") $mod:struct module*
kernel.trace("ext4:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("ext4:module_request") $name:char* $wait:bool $ip:long unsigned
int
# stap -L 'kernel.trace("skb:module*")'
kernel.trace("skb:module_free") $mod:struct module*
kernel.trace("skb:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("skb:module_load") $mod:struct module*
kernel.trace("skb:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("skb:module_request") $name:char* $wait:bool $ip:long unsigned int
# stap -L 'kernel.trace("net:module*")'
kernel.trace("net:module_free") $mod:struct module*
kernel.trace("net:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("net:module_load") $mod:struct module*
kernel.trace("net:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("net:module_request") $name:char* $wait:bool $ip:long unsigned int
# stap -L 'kernel.trace("block:module*")'
kernel.trace("block:module_free") $mod:struct module*
kernel.trace("block:module_get") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("block:module_load") $mod:struct module*
kernel.trace("block:module_put") $mod:struct module* $ip:long unsigned int
$refcnt:int
kernel.trace("block:module_request") $name:char* $wait:bool $ip:long unsigned
int
====
Also note this isn't just because I used a wildcard, since the following works:
====
# stap -L 'kernel.trace("block:module_free")'
kernel.trace("block:module_free") $mod:struct module*
====
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