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Cause
The uprobe.ko kernel module is needed when probing a user-space module.
This uprobes.ko kernel module is built if none currently exists. This can
lead to a race condition when multiple scripts probing user-space
applications note a uprobes.ko kernel module needs to be built
Consequence
The multiple parallel builds of uprobes.ko can interfere with each other
and cause the scripts to fail to build and run.
Fix
The stap command now caches the resulting uprobe kernel module
like other systemtap instrumentation to avoid interferring with
systemtap instrumentation instances.
Result
Multiple systemtap scripts probing userspace applications will not
interfere with each other regardless whether a uprobe.ko kernel
module exists.
Description of problem:
If two systemtap scripts are run simultaneously on a fresh system
they can clash when trying to rebuild uprobes.ko.
Version-Release number of selected component (if applicable):
systemtap-1.2-9.el6.x86_64
Steps to Reproduce:
stap script1.stp & stap script2.stp
Actual results:
The failure can look like this:
> Pass 1: parsed user script and 69 library script(s) using 83956virt/20868res/2424shr kb, in 130usr/10sys/142real ms.
> Pass 1: parsed user script and 69 library script(s) using 83960virt/20880res/2424shr kb, in 140usr/20sys/157real ms.
> Pass 2: analyzed script: 2 probe(s), 13 function(s), 4 embed(s), 2 global(s) using 93988virt/25276res/4248shr kb, in 710usr/1090sys/5767real ms.
> Pass 2: analyzed script: 2 probe(s), 6 function(s), 3 embed(s), 1 global(s) using 94092virt/25260res/4248shr kb, in 680usr/1090sys/5694real ms.
> Pass 3: translated to C into "/tmp/stapGoohFi/stap_45c4d31c9a6fd424692598f20d205124_5605.c" using 93820virt/25404res/4352shr kb, in 40usr/170sys/235real ms.
> Pass 4, preamble: (re)building SystemTap's version of uprobes.
> Pass 3: translated to C into "/tmp/stapDuYGzm/stap_c2ecdfd215a17ee48c16da7c15076a09_3797.c" using 93804virt/25388res/4356shr kb, in 60usr/170sys/224real ms.
> Pass 4, preamble: (re)building SystemTap's version of uprobes.
> mv: cannot stat `/usr/share/systemtap/runtime/uprobes/.tmp_mx_uprobes.o': No such file or directory
> rm: cannot remove `/usr/share/systemtap/runtime/uprobes/.tmp_mc_uprobes.o': No such file or directory
> rm: cannot remove `/usr/share/systemtap/runtime/uprobes/.tmp_mc_uprobes.s': No such file or directory
> mv: cannot stat `/usr/share/systemtap/runtime/uprobes/.uprobes.o.tmp': No such file or directory
> make[3]: *** [/usr/share/systemtap/runtime/uprobes/uprobes.o] Error 1
> make[2]: *** [_module_/usr/share/systemtap/runtime/uprobes] Error 2
> make[1]: *** [default] Error 2
> Pass 4: compiled C into "stap_45c4d31c9a6fd424692598f20d205124_5605.ko" in 1400usr/510sys/2254real ms.
> Pass 4: compilation failed. Try again with another '--vp 0001' option.
> make[2]: *** Deleting file `/tmp/stapDuYGzm/stapconf_665804123654012ea35c70fb0980ad69_518.h'
> make[2]: *** [/tmp/stapDuYGzm/stapconf_665804123654012ea35c70fb0980ad69_518.h] Terminated
> make[1]: *** [_module_/tmp/stapDuYGzm] Terminated
> Pass 4: compiled C into "stap_c2ecdfd215a17ee48c16da7c15076a09_3797.ko" in 2590usr/1140sys/4196real ms.
> Pass 4: compilation failed. Try again with another '--vp 0001' option.
Expected results:
No collision.
If this is not a regression, I would suggest postponing to 6.2. This has a trivial workaround.
Comment 2RHEL Program Management
2011-04-04 01:54:38 UTC
Since RHEL 6.1 External Beta has begun, and this bug remains
unresolved, it has been rejected as it is not proposed as
exception or blocker.
Red Hat invites you to ask your support representative to
propose this request, if appropriate and relevant, in the
next release of Red Hat Enterprise Linux.
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
New Contents:
Cause
The uprobe.ko kernel module is needed when probing a user-space module.
This uprobes.ko kernel module is built if none currently exists. This can
lead to a race condition when multiple scripts probing user-space
applications note a uprobes.ko kernel module needs to be built
Consequence
The multiple parallel builds of uprobes.ko can interfere with each other
and cause the scripts to fail to build and run.
Fix
The stap command now caches the resulting uprobe kernel module
like other systemtap instrumentation to avoid interferring with
systemtap instrumentation instances.
Result
Multiple systemtap scripts probing userspace applications will not
interfere with each other regardless whether a uprobe.ko kernel
module exists.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
http://rhn.redhat.com/errata/RHBA-2011-1517.html
Description of problem: If two systemtap scripts are run simultaneously on a fresh system they can clash when trying to rebuild uprobes.ko. Version-Release number of selected component (if applicable): systemtap-1.2-9.el6.x86_64 Steps to Reproduce: stap script1.stp & stap script2.stp Actual results: The failure can look like this: > Pass 1: parsed user script and 69 library script(s) using 83956virt/20868res/2424shr kb, in 130usr/10sys/142real ms. > Pass 1: parsed user script and 69 library script(s) using 83960virt/20880res/2424shr kb, in 140usr/20sys/157real ms. > Pass 2: analyzed script: 2 probe(s), 13 function(s), 4 embed(s), 2 global(s) using 93988virt/25276res/4248shr kb, in 710usr/1090sys/5767real ms. > Pass 2: analyzed script: 2 probe(s), 6 function(s), 3 embed(s), 1 global(s) using 94092virt/25260res/4248shr kb, in 680usr/1090sys/5694real ms. > Pass 3: translated to C into "/tmp/stapGoohFi/stap_45c4d31c9a6fd424692598f20d205124_5605.c" using 93820virt/25404res/4352shr kb, in 40usr/170sys/235real ms. > Pass 4, preamble: (re)building SystemTap's version of uprobes. > Pass 3: translated to C into "/tmp/stapDuYGzm/stap_c2ecdfd215a17ee48c16da7c15076a09_3797.c" using 93804virt/25388res/4356shr kb, in 60usr/170sys/224real ms. > Pass 4, preamble: (re)building SystemTap's version of uprobes. > mv: cannot stat `/usr/share/systemtap/runtime/uprobes/.tmp_mx_uprobes.o': No such file or directory > rm: cannot remove `/usr/share/systemtap/runtime/uprobes/.tmp_mc_uprobes.o': No such file or directory > rm: cannot remove `/usr/share/systemtap/runtime/uprobes/.tmp_mc_uprobes.s': No such file or directory > mv: cannot stat `/usr/share/systemtap/runtime/uprobes/.uprobes.o.tmp': No such file or directory > make[3]: *** [/usr/share/systemtap/runtime/uprobes/uprobes.o] Error 1 > make[2]: *** [_module_/usr/share/systemtap/runtime/uprobes] Error 2 > make[1]: *** [default] Error 2 > Pass 4: compiled C into "stap_45c4d31c9a6fd424692598f20d205124_5605.ko" in 1400usr/510sys/2254real ms. > Pass 4: compilation failed. Try again with another '--vp 0001' option. > make[2]: *** Deleting file `/tmp/stapDuYGzm/stapconf_665804123654012ea35c70fb0980ad69_518.h' > make[2]: *** [/tmp/stapDuYGzm/stapconf_665804123654012ea35c70fb0980ad69_518.h] Terminated > make[1]: *** [_module_/tmp/stapDuYGzm] Terminated > Pass 4: compiled C into "stap_c2ecdfd215a17ee48c16da7c15076a09_3797.ko" in 2590usr/1140sys/4196real ms. > Pass 4: compilation failed. Try again with another '--vp 0001' option. Expected results: No collision.