path: root/usr/src/man/man3c_db/td_sync_get_info.3c_db

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.TH TD_SYNC_GET_INFO 3C_DB "Nov 22, 2018"
.SH 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
.SH SYNOPSIS
.LP
.nf
cc [ \fIflag\fR... ] \fIfile\fR... -lc_db [ \fIlibrary\fR... ]
#include <proc_service.h>
#include <thread_db.h>

\fBtd_err_e\fR \fBtd_sync_get_info\fR(\fBconst td_synchandle_t *\fR\fIsh_p\fR, \fBtd_syncinfo_t *\fR\fIsi_p\fR);
.fi

.LP
.nf
\fBtd_err_e\fR \fBtd_ta_sync_tracking_enable\fR(\fBconst td_thragent_t *\fR\fIta_p\fR, \fBint\fR \fIon_off\fR);
.fi

.LP
.nf
\fBtd_err_e\fR \fBtd_sync_get_stats\fR(\fBconst td_synchandle_t *\fR\fIsh_p\fR, \fBtd_syncstats_t *\fR\fIss_p\fR);
.fi

.LP
.nf
\fBtd_err_e\fR \fBtd_sync_setstate\fR(\fBconst td_synchandle_t *\fR\fIsh_p\fR, \fBint\fR \fIvalue\fR);
.fi

.LP
.nf
\fBtypedef int\fR \fBtd_thr_iter_f\fR(\fBconst td_thrhandle_t *\fR\fIth_p\fR, \fBvoid *\fR\fIcb_data_p\fR);
.fi

.LP
.nf
\fBtd_err_e\fR \fBtd_sync_waiters\fR(\fBconst td_synchandle_t *\fR\fIsh_p\fR, \fBtd_thr_iter_f *\fR\fIcb\fR,
     \fBvoid *\fR\fIcb_data_p\fR);
.fi

.SH DESCRIPTION
.sp
.LP
Synchronization objects include mutexes, condition variables, semaphores, and
reader-writer locks. In the same way that thread operations use a thread handle
of type \fBtd_thrhandle_t\fR, operations on synchronization objects use a
synchronization object handle of type \fBtd_synchandle_t\fR.
.sp
.LP
The controlling process obtains synchronization object handles either by
calling the function \fBtd_ta_sync_iter()\fR to obtain handles for all
synchronization objects of the target process that are known to the
\fBlibc_db\fR library of interfaces, or by mapping the address of a
synchronization object in the address space of the target process to a handle
by calling \fBtd_ta_map_addr2sync\fR(3C_DB).
.sp
.LP
Not all synchronization objects that a process uses can be known to the
\fBlibc_db\fR library and returned by \fBtd_ta_sync_iter\fR(3C_DB). A
synchronization object is known to \fBlibc_db\fR only if it has been the target
of a synchronization primitive in the process (such as \fBmutex_lock()\fR,
described on the \fBmutex_init\fR(3C) manual page) after \fBtd_ta_new\fR(3C_DB)
has been called to attach to the process and \fBtd_ta_sync_tracking_enable()\fR
has been called to enable synchronization object tracking.
.sp
.LP
The \fBtd_ta_sync_tracking_enable()\fR function turns synchronization object
tracking on or off for the process identified by \fIta_p\fR, depending on
whether \fIon_off\fR is 0 (off) or non-zero (on).
.sp
.LP
The \fBtd_sync_get_info()\fR function fills in the \fBtd_syncinfo_t\fR
structure \fB*\fR\fIsi_p\fR with values for the synchronization object
identified by  \fBsh_p\fR. The \fBtd_syncinfo_t\fR structure contains the
following fields:
.sp
.ne 2
.na
\fB\fBtd_thragent_t *\fR\fIsi_ta_p\fR\fR
.ad
.RS 29n
The internal process handle identifying the target process through which this
synchronization 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.
.RE

.sp
.ne 2
.na
\fB\fBpsaddr_t\fR \fIsi_sv_addr\fR\fR
.ad
.RS 29n
The address of the synchronization object in this target process's address
space.
.RE

.sp
.ne 2
.na
\fB\fBtd_sync_type_e\fR \fIsi_type\fR\fR
.ad
.RS 29n
The type of the synchronization variable: mutex, condition variable, semaphore,
or readers-writer lock.
.RE

.sp
.ne 2
.na
\fB\fBint\fR \fIsi_shared_type\fR\fR
.ad
.RS 29n
If \fIsi_shared_type\fR is non-zero, this synchronization object is
process-shared, otherwise it is process-private.
.RE

.sp
.ne 2
.na
\fB\fBtd_sync_flags_t\fR \fIsi_flags\fR\fR
.ad
.RS 29n
Flags dependent on the type of the synchronization object.
.RE

.sp
.ne 2
.na
\fB\fBint\fR \fIsi_state.sema_count\fR\fR
.ad
.RS 29n
Semaphores only.  The current value of the semaphore
.RE

.sp
.ne 2
.na
\fB\fBint\fR \fIsi_state.nreaders\fR\fR
.ad
.RS 29n
Readers-writer locks only. The number of readers currently holding the lock, or
\fB-1\fR, if a writer is currently holding the lock.
.RE

.sp
.ne 2
.na
\fB\fBint\fR \fIsi_state.mutex_locked\fR\fR
.ad
.RS 29n
For mutexes only. Non-zero if and only if the mutex is currently locked.
.RE

.sp
.ne 2
.na
\fB\fBint\fR \fIsi_size\fR\fR
.ad
.RS 29n
The size of the synchronization object.
.RE

.sp
.ne 2
.na
\fB\fBuint8_t\fR \fIsi_has_waiters\fR\fR
.ad
.RS 29n
Non-zero if and only if at least one thread is blocked on this synchronization
object.
.RE

.sp
.ne 2
.na
\fB\fBuint8_t\fR \fIsi_is_wlocked\fR\fR
.ad
.RS 29n
For reader-writer locks only. The value is non-zero if and only if this lock is
held by a writer.
.RE

.sp
.ne 2
.na
\fB\fBuint8_t\fR \fIsi_rcount\fR\fR
.ad
.RS 29n
\fBPTHREAD_MUTEX_RECURSIVE\fR mutexes only. If the mutex is held, the recursion
count.
.RE

.sp
.ne 2
.na
\fB\fBuint8_t\fR \fIsi_prioceiling\fR\fR
.ad
.RS 29n
\fBPTHREAD_PRIO_PROTECT\fR protocol mutexes only. The priority ceiling.
.RE

.sp
.ne 2
.na
\fB\fBtd_thrhandle_t\fR \fIsi_owner\fR\fR
.ad
.RS 29n
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    \fINULL\fR if
no one holds the mutex or write-lock.
.RE

.sp
.ne 2
.na
\fB\fBpid_t\fR \fIsi_ownerpid\fR\fR
.ad
.RS 29n
Mutexes only.  For a locked process-shared mutex, this is the process-ID of the
process containing the owning thread.
.RE

.sp
.LP
The \fBtd_sync_get_stats()\fR function fills in the \fBtd_syncstats_t\fR
structure *\fIss_p\fR with values for the synchronization object identified by
\fIsh_p\fR.  The \fBtd_syncstats_t\fR structure contains an embedded
\fBtd_syncinfo_t\fR structure that is filled in as described above for
\fBtd_sync_get_info()\fR.  In addition, usage statistics gathered since
\fBtd_ta_sync_tracking_enable()\fR was called to enable synchronization object
tracking are returned in the \fBss_un.mutex\fR, \fBss_un.cond\fR,
\fBss_un.rwlock\fR, or \fBss_un.sema\fR members of the \fBtd_syncstats_t\fR
structure, depending on the type of the synchronization object.
.sp
.LP
The \fBtd_sync_setstate\fR function modifies the state of synchronization
object \fIsi_p\fR, depending on the synchronization object type. For mutexes,
\fBtd_sync_setstate\fR is unlocked if the \fIvalue\fR is \fB0\fR. Otherwise it
is locked. For semaphores, the semaphore's count is set to the \fIvalue\fR. For
reader-writer locks, the reader count set to the \fIvalue\fR if \fIvalue\fR is
\fB>0\fR. The count is set to write-locked if \fIvalue\fR is \fB-1\fR\&.
It is set to unlocked if the \fIvalue\fR is \fB0\fR. Setting the state of a
synchronization object from a \fBlibc_db\fR 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 \fBtd_sync_setstate\fR is used to set the mutex to unlocked, then a
different thread  will also be able to subsequently acquire the same mutex.
.sp
.LP
The \fBtd_sync_waiters\fR function iterates over the set of thread handles of
threads blocked on \fIsh_p\fR. The callback function \fIcb\fR is called once
for each such thread handle, and is passed  the thread handle and
\fIcb_data_p\fR. If the callback function returns a non-zero value, iteration
is terminated early. See \fBtd_ta_thr_iter\fR(3C_DB).
.SH RETURN VALUES
.sp
.ne 2
.na
\fB\fBTD_OK\fR \fR
.ad
.RS 13n
The call returned successfully.
.RE

.sp
.ne 2
.na
\fB\fBTD_BADTH\fR \fR
.ad
.RS 13n
An invalid thread handle was passed in.
.RE

.sp
.ne 2
.na
\fB\fBTD_DBERR\fR \fR
.ad
.RS 13n
A call to one of the imported interface routines failed.
.RE

.sp
.ne 2
.na
\fB\fBTD_ERR\fR \fR
.ad
.RS 13n
A libc_db-internal error occurred.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT-Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBlibc_db\fR(3LIB), \fBmutex_init\fR(3C), \fBtd_ta_map_addr2sync\fR(3C_DB),
\fBtd_ta_sync_iter\fR(3C_DB), \fBtd_ta_thr_iter\fR(3C_DB), \fBattributes\fR(7)