[SCM] systemtap: system-wide probe/trace tool branch, master, updated. release-1.0-114-g720bbfc

[SCM] systemtap: system-wide probe/trace tool branch, master, updated. release-1.0-114-g720bbfc

[srikar]

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      from  3c2341daf979fc38fc534ae91e00594a525962e0 (commit)

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- Log -----------------------------------------------------------------
commit 720bbfc68d9e7dfd8c37587c6a61da75d6aab4fa
Author: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Date:   Mon Oct 19 13:44:21 2009 +0530

    Avoid lockdep warnings.
    
    uprobe_fork_uproc() runs with parent_uproc->rwsem locked.
    However uprobe_mk_process() that gets called within uprobe_fork_uproc()
    also locks child_uproc->rwsem after initializing it.
    
    Lockdep report confuses this to acquiring a lock that already has been
    acquired and suggests using sub-classes.
    
    The alternatives we have are:
    1. use classes level to distinguish different uproc structures.
    2. unlock parent_uproc->rwsem before we call uprobe_fork_uproc().
    3. dont try locking child_uproc->rwsem; since we are protected by
       uproc_mutex as well as parent_uproc->rwsem;
    
    We use the last approach.
    
    Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    ---

-----------------------------------------------------------------------

Summary of changes:
 runtime/uprobes/uprobes.c  |   24 +++++++++++++++++-------
 runtime/uprobes2/uprobes.c |   24 +++++++++++++++++-------
 2 files changed, 34 insertions(+), 14 deletions(-)


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systemtap: system-wide probe/trace tool