pthdb_session_committed Subroutines

Purpose

Facilitates examining and modifying multi-threaded application's pthread library object data.

Library

pthread debug library (libpthdebug.a)

Syntax

#include <sys/pthdebug.h>

int pthdb_session_committed (pthdb_session_t  session,
                             char            ** name);
int pthdb_session_concurrency (pthdb_session_t  session,
                               int             * concurrencyp);
int pthdb_session_destroy (pthdb_session_t  session)
int pthdb_session_flags (pthdb_session_t session,
                         unsigned long long * flagsp)
int pthdb_session_init (pthdb_user_t  user,
                        pthdb_exec_mode_t  exec_mode,
                        unsigned long long  flags,
                        pthdb_callbacks_t * callbacks,
                        pthdb_session_t * sessionp)
int pthdb_session_pthreaded (pthdb_user_t   user,
                             unsigned long long  flags
                             pthdb_callbacks_t * callbacks,
                             char              ** name)
int pthdb_session_continue_tid (pthdb_session_t  session,
                                tid_t           * tidp,
                                int              cmd);
int pthdb_session_stop_tid (pthdb_session_t  session,
                            tid_t            tid);
int pthdb_session_commit_tid (pthdb_session_t  session,
                              tid_t           * tidp,
                              int               cmd);
int pthdb_session_setflags (pthdb_session_t     session,
                            unsigned long long  flags)
int pthdb_session_update (pthdb_session_t  session)

Description

To facilitate debugging multiple processes, the pthread debug library supports multiple sessions, one per process. Functions are provided to initialize, destroy, and customize the behavior of these sessions. In addition, functions are provided to query global fields of the pthread library. All functions in the library require a session handle associated with an initialized session except pthdb_session_init, which initializes sessions, and pthdb_session_pthreaded, which can be called before the session has been initialized.

pthdb_session_committed reports the symbol name of a function called after the hold/unhold commit operation has completed. This symbol name can be used to set a breakpoint to notify the debugger when the hold/unhold commit has completed. The actual symbol name reported may change at any time. The function name returned is implemented in assembly with the following code:

                ori 0,0, 0         # no-op
                blr                # return to caller

This allows the debugger to overwrite the no-op with a trap instruction and leave it there by stepping over it. This function is only supported when the PTHDB_FLAG_HOLD flag is set.

pthdb_session_concurrency reports the concurrency level of the pthread library. The concurrency level is the M:N ratio, where N is always 1.

pthdb_session_destroy notifies the pthread debug library that the debugger or application is finished with the session. This deallocates any memory associated with the session and allows the session handle to be reused.

pthdb_session_setflags changes the flags for a session. With these flags, a debugger can customize the session. Flags consist of the following values or-ed together:

The pthdb_session_flags function gets the current flags for the session.

The pthdb_session_init function tells the pthread debug library to initialize a session associated with the unique given user handle. pthdb_session_init will assign a unique session handle and return it to the debugger. If the application's execution mode is 32 bit, then the debugger should initialize the exec_mode to PEM_32BIT. If the application's execution mode is 64 bit, then the debugger should initialize mode to PEM_64BIT. The flags are documented above with the pthdb_session_setflags function. The callback parameter is a list of call back functions. (Also see the pthdebug.h header file.) The pthdb_session_init function calls the symbol_addrs function to get the starting addresses of the symbols and initializes these symbols' starting addresses within the pthread debug library.

pthdb_session_pthreaded reports the symbol name of a function called after the pthread library has been initialized. This symbol name can be used to set a breakpoint to notify the debugger when to initialize a pthread debug library session and begin using the pthread debug library to examine pthread library state. The actual symbol name reported may change at any time. This function, is the only pthread debug library function that can be called before the pthread library is initialized. The function name returned is implemented in assembly with the following code:

                ori 0,0,0           # no-op
                blr                 # return to caller

This is conveniently allows the debugger to overwrite the no-op with a trap instruction and leave it there by stepping over it.

The pthdb_session_continue_tid function allows the debugger to obtain the list of threads that must be continued before it proceeds with single stepping a single pthread or continuing a group of pthreads. This function reports one tid at a time. If the list is empty or the end of the list has been reached, PTHDB_INVALID_TID is reported. The debugger will need to continue any pthreads with kernel threads that it wants. The debugger is responsible for parking the stop thread and continuing the stop thread. The cmd parameter can be either PTHDB_LIST_NEXT or PTHDB_LIST_FIRST; if PTHDB_LIST_FIRST is passed, then the internal counter will be reset and the first tid in the list will be reported.

The pthdb_session_stop_tid function informs the pthread debug library, which informs the pthread library the tid of the thread that stopped the debugger.

pthdb_session_commit_tid reports subsequent kernel thread identifiers which must be continued to commit the hold and unhold changes. This function reports one tid at a time. If the list is empty or the end of the list has been reached, PTHDB_INVALID_TID is reported. The cmd parameter can be either PTHDB_LIST_NEXT or PTHDB_LIST_FIRST, if PTHDB_LIST_FIRST is passed then the internal counter will be reset and first tid in the list will be reported.

pthdb_session_update tells the pthread debug library to update it's internal information concerning the state of the pthread library. This should be called each time the process stops before any other pthread debug library functions to ensure their results are reliable.

Each list is reset to the top of the list when the pthdb_session_update function is called, or when the list function reports a PTHDB_INVALID_* value. For example, when pthdb_attr reports an attribute of PTHDB_INVALID_ATTR the list is reset to the beginning such that the next call reports the first attribute in the list, if any.

A report of PTHDB_INVALID_OBJECT represents the empty list or the end of a list, where OBJECT is one of these values: PTHREAD, ATTR, MUTEX, MUTEXATTR, COND, CONDATTR, RWLOCK, RWLOCKATTR, KEY, or TID as appropriate.

Parameters

Return Values

If successful, these functions return PTHDB_SUCCESS. Otherwise, they return an error value.

Error Codes