TD_SYNC_GET_INFO(3C_DB)TD_SYNC_GET_INFO(3C_DB)NAME
td_sync_get_info, td_ta_sync_tracking_enable, td_sync_get_stats,
td_sync_setstate, td_sync_waiters - operations on a synchronization
object in libc_db
SYNOPSIS
cc [ flag... ] file... -lc_db [ library... ]
#include <proc_service.h>
#include <thread_db.h>
td_err_e td_sync_get_info(const td_synchandle_t *sh_p, td_syncinfo_t *si_p);
td_err_e td_ta_sync_tracking_enable(const td_thragent_t *ta_p, int on_off);
td_err_e td_sync_get_stats(const td_synchandle_t *sh_p, td_syncstats_t *ss_p);
td_err_e td_sync_setstate(const td_synchandle_t *sh_p);
typedef int td_thr_iter_f(const td_thrhandle_t *th_p, void *cb_data_p);
td_err_e td_sync_waiters(const td_synchandle_t *sh_p, td_thr_iter_f *cb,
void *cb_data_p);
DESCRIPTION
Synchronization objects include mutexes, condition variables, sema‐
phores, and reader-writer locks. In the same way that thread operations
use a thread handle of type td_thrhandle_t, operations on synchroniza‐
tion objects use a synchronization object handle of type td_synchan‐
dle_t.
The controlling process obtains synchronization object handles either
by calling the function td_ta_sync_iter() to obtain handles for all
synchronization objects of the target process that are known to the
libc_db library of interfaces, or by mapping the address of a synchro‐
nization object in the address space of the target process to a handle
by calling td_ta_map_addr2sync(3C_DB).
Not all synchronization objects that a process uses can be known to the
libc_db library and returned by td_ta_sync_iter(3C_DB). A synchroniza‐
tion object is known to libc_db only if it has been the target of a
synchronization primitive in the process (such as mutex_lock(),
described on the mutex_init(3C) manual page) after td_ta_new(3C_DB) has
been called to attach to the process and td_ta_sync_tracking_enable()
has been called to enable synchronization object tracking.
The td_ta_sync_tracking_enable() function turns synchronization object
tracking on or off for the process identified by ta_p, depending on
whether on_off is 0 (off) or non-zero (on).
The td_sync_get_info() function fills in the td_syncinfo_t structure
*si_p with values for the synchronization object identified by sh_p.
The td_syncinfo_t structure contains the following fields:
td_thragent_t *si_ta_p
The internal process handle identifying
the target process through which this syn‐
chronization object handle was obtained.
Synchronization objects may be process-
private or process-shared. In the latter
case, the same synchronization object may
have multiple handles, one for each target
process's "view" of the synchronization
object.
psaddr_t si_sv_addr
The address of the synchronization object
in this target process's address space.
td_sync_type_e si_type
The type of the synchronization variable:
mutex, condition variable, semaphore, or
readers-writer lock.
int si_shared_type
If si_shared_type is non-zero, this syn‐
chronization object is process-shared,
otherwise it is process-private.
td_sync_flags_t si_flags
Flags dependent on the type of the syn‐
chronization object.
int si_state.sema_count
Semaphores only. The current value of the
semaphore
int si_state.nreaders
Readers-writer locks only. The number of
readers currently holding the lock, or -1,
if a writer is currently holding the lock.
int si_state.mutex_locked
For mutexes only. Non-zero if and only if
the mutex is currently locked.
int si_size
The size of the synchronization object.
uint8_t si_has_waiters
Non-zero if and only if at least one
thread is blocked on this synchronization
object.
uint8_t si_is_wlocked
For reader-writer locks only. The value is
non-zero if and only if this lock is held
by a writer.
uint8_t si_rcount
PTHREAD_MUTEX_RECURSIVE mutexes only. If
the mutex is held, the recursion count.
uint8_t si_prioceiling
PTHREAD_PRIO_PROTECT protocol mutexes
only. The priority ceiling.
td_thrhandle_t si_owner
Mutexes and readers-writer locks only.
This is the thread holding the mutex, or
the write lock, if this is a reader-writer
lock. The value is NULL if no one holds
the mutex or write-lock.
pid_t si_ownerpid
Mutexes only. For a locked process-shared
mutex, this is the process-ID of the
process containing the owning thread.
The td_sync_get_stats() function fills in the td_syncstats_t structure
*ss_p with values for the synchronization object identified by sh_p.
The td_syncstats_t structure contains an embedded td_syncinfo_t struc‐
ture that is filled in as described above for td_sync_get_info(). In
addition, usage statistics gathered since td_ta_sync_tracking_enable()
was called to enable synchronization object tracking are returned in
the ss_un.mutex, ss_un.cond, ss_un.rwlock, or ss_un.sema members of the
td_syncstats_t structure, depending on the type of the synchronization
object.
The td_sync_setstate function modifies the state of synchronization
object si_p, depending on the synchronization object type. For mutexes,
td_sync_setstate is unlocked if the value is 0. Otherwise it is
locked. For semaphores, the semaphore's count is set to the value. For
reader-writer locks, the reader count set to the value if value is >0.
The count is set to write-locked if value is -1. It is set to unlocked
if the value is 0. Setting the state of a synchronization object from
a libc_db interface may cause the synchronization object's semantics to
be violated from the point of view of the threads in the target
process. For example, if a thread holds a mutex, and td_sync_setstate
is used to set the mutex to unlocked, then a different thread will
also be able to subsequently acquire the same mutex.
The td_sync_waiters function iterates over the set of thread handles of
threads blocked on sh_p. The callback function cb is called once for
each such thread handle, and is passed the thread handle and
cb_data_p. If the callback function returns a non-zero value, iteration
is terminated early. See td_ta_thr_iter(3C_DB).
RETURN VALUES
TD_OK
The call returned successfully.
TD_BADTH
An invalid thread handle was passed in.
TD_DBERR
A call to one of the imported interface routines failed.
TD_ERR
A libc_db-internal error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT-Level │ Safe │
└───────────────┴─────────────────┘
SEE ALSOlibc_db(3LIB), mutex_init(3C), td_ta_map_addr2sync(3C_DB),
td_ta_sync_iter(3C_DB), td_ta_thr_iter(3C_DB), attributes(5)
Jun 5, 2007 TD_SYNC_GET_INFO(3C_DB)
