[Bug runtime/17181] New: systemtap has problems attaching to resumed processes

[Bug runtime/17181] New: systemtap has problems attaching to resumed processes

[dsmith at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17181

            Bug ID: 17181
           Summary: systemtap has problems attaching to resumed processes
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: dsmith at redhat dot com

Systemtap will error when attempting to attach to a resumed process. This
happens with "fake" utrace (seen on RHEL7 and f20).

====
# stap -v -e 'probe syscall.getpid { printf("%s\n", probefunc()) }'
<snip>
Pass 5: starting run.
sys_getpid
<snip>
ERROR: utrace_set_events returned error -114 on pid 1903
WARNING: /usr/bin/staprun exited with status: 1
Pass 5: run completed in 0usr/70sys/8196real ms.
Pass 5: run failed.  [man error::pass5]
====

Here's how to reproduce this one:

1. Compile the following C code to 'a.out'.
====
#include <unistd.h>
#include <signal.h>

void main()
{
    kill(getpid(), SIGSTOP);
    getpid();
}
====

2. Run 'a.out' in the background.

# ./a.out &
[1] <pid>

3. Execute stap command in another console.
# stap -v -e 'probe syscall.getpid { printf("%s\n", probefunc()) }'

4. Resume the stopped process
# kill -cont <pid>

Sometimes the stopped process can get stuck in the 't' state till
kill -9'd.

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[Bug runtime/17181] systemtap has problems attaching to resumed processes

[dsmith at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17181

--- Comment #1 from David Smith <dsmith at redhat dot com> ---
Note that this one is somewhat related to bug #17127. I know believe the fix
there wasn't right.

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[Bug runtime/17181] systemtap has problems attaching to resumed processes

[dsmith at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17181

David Smith <dsmith at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from David Smith <dsmith at redhat dot com> ---
Fixed in commit d9d07e9, which also adds a testcase. Basically our utrace
wasn't interrupting processes properly.

Note that this commit reverts the bug #17127 fix.

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