Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #109
Difficulty: Easy
The Unix shell is the interface between the user and the kernel.
True or False?
Linux & Unix Commands - Search Man Pages

qwait(9f) [bsd man page]

qwait(9F)						   Kernel Functions for Drivers 						 qwait(9F)

NAME
qwait, qwait_sig - STREAMS wait routines SYNOPSIS
#include <sys/stream.h> #include <sys/ddi.h> void qwait(queue_t *q); int qwait_sig(queue_t *q); INTERFACE LEVEL
Solaris DDI specific (Solaris DDI). PARAMETERS
qp Pointer to the queue that is being opened or closed. DESCRIPTION
qwait() and qwait_sig() are used to wait for a message to arrive to the put(9E) or srv(9E) procedures. qwait() and qwait_sig() can also be used to wait for qbufcall(9F) or qtimeout(9F) callback procedures to execute. These routines can be used in the open(9E) and close(9E) pro- cedures in a STREAMS driver or module. Note - The thread that calls close() does not necessarily have the ability to receive signals, particularly when called by exit(2). In this case, qwait_sig() behaves exactly as qwait(). Driver writers may use ddi_can_receive_sig(9F) to determine when this is the case, and, if so, arrange some means to avoid blocking indefinitely (for example, by using qtimeout(9F). qwait() and qwait_sig() atomically exit the inner and outer perimeters associated with the queue, and wait for a thread to leave the mod- ule's put(9E), srv(9E), or qbufcall(9F) / qtimeout(9F) callback procedures. Upon return they re-enter the inner and outer perimeters. This can be viewed as there being an implicit wakeup when a thread leaves a put(9E) or srv(9E) procedure or after a qtimeout(9F) or qbuf- call(9F) callback procedure has been run in the same perimeter. qprocson(9F) must be called before calling qwait() or qwait_sig(). qwait() is not interrupted by a signal, whereas qwait_sig() is interrupted by a signal. qwait_sig() normally returns non-zero, and returns zero when the waiting was interrupted by a signal. qwait() and qwait_sig() are similar to cv_wait() and cv_wait_sig() except that the mutex is replaced by the inner and outer perimeters and the signalling is implicit when a thread leaves the inner perimeter. See condvar(9F). RETURN VALUES
0 For qwait_sig(), indicates that the condition was not necessarily signaled, and the function returned because a signal was pend- ing. CONTEXT
These functions can only be called from an open(9E) or close(9E) routine. EXAMPLES
Example 1: Using qwait() The open routine sends down a T_INFO_REQ message and waits for the T_INFO_ACK. The arrival of the T_INFO_ACK is recorded by resetting a flag in the unit structure (WAIT_INFO_ACK). The example assumes that the module is D_MTQPAIR or D_MTPERMOD. xxopen(qp, ...) queue_t *qp; { struct xxdata *xx; /* Allocate xxdata structure */ qprocson(qp); /* Format T_INFO_ACK in mp */ putnext(qp, mp); xx->xx_flags |= WAIT_INFO_ACK; while (xx->xx_flags & WAIT_INFO_ACK) qwait(qp); return(0); } xxrput(qp, mp) queue_t *qp; mblk_t *mp; { struct xxdata *xx = (struct xxdata *)q->q_ptr; ... case T_INFO_ACK: if (xx->xx_flags & WAIT_INFO_ACK) { /* Record information from info ack */ xx->xx_flags &= ~WAIT_INFO_ACK; freemsg(mp); return; } ... } SEE ALSO
close(9E), open(9E), put(9E), srv(9E), condvar(9F), ddi_can_receive_sig(9F), mt-streams(9F), qbufcall(9F), qprocson(9F), qtimeout(9F) STREAMS Programming Guide Writing Device Drivers SunOS 5.10 15 Dec 2003 qwait(9F)

Check Out this Related Man Page

qwait(9F)						   Kernel Functions for Drivers 						 qwait(9F)

NAME
qwait, qwait_sig - STREAMS wait routines SYNOPSIS
#include <sys/stream.h> #include <sys/ddi.h> void qwait(queue_t *q); int qwait_sig(queue_t *q); INTERFACE LEVEL
Solaris DDI specific (Solaris DDI). PARAMETERS
qp Pointer to the queue that is being opened or closed. DESCRIPTION
qwait() and qwait_sig() are used to wait for a message to arrive to the put(9E) or srv(9E) procedures. qwait() and qwait_sig() can also be used to wait for qbufcall(9F) or qtimeout(9F) callback procedures to execute. These routines can be used in the open(9E) and close(9E) pro- cedures in a STREAMS driver or module. Note - The thread that calls close() does not necessarily have the ability to receive signals, particularly when called by exit(2). In this case, qwait_sig() behaves exactly as qwait(). Driver writers may use ddi_can_receive_sig(9F) to determine when this is the case, and, if so, arrange some means to avoid blocking indefinitely (for example, by using qtimeout(9F). qwait() and qwait_sig() atomically exit the inner and outer perimeters associated with the queue, and wait for a thread to leave the mod- ule's put(9E), srv(9E), or qbufcall(9F) / qtimeout(9F) callback procedures. Upon return they re-enter the inner and outer perimeters. This can be viewed as there being an implicit wakeup when a thread leaves a put(9E) or srv(9E) procedure or after a qtimeout(9F) or qbuf- call(9F) callback procedure has been run in the same perimeter. qprocson(9F) must be called before calling qwait() or qwait_sig(). qwait() is not interrupted by a signal, whereas qwait_sig() is interrupted by a signal. qwait_sig() normally returns non-zero, and returns zero when the waiting was interrupted by a signal. qwait() and qwait_sig() are similar to cv_wait() and cv_wait_sig() except that the mutex is replaced by the inner and outer perimeters and the signalling is implicit when a thread leaves the inner perimeter. See condvar(9F). RETURN VALUES
0 For qwait_sig(), indicates that the condition was not necessarily signaled, and the function returned because a signal was pend- ing. CONTEXT
These functions can only be called from an open(9E) or close(9E) routine. EXAMPLES
Example 1: Using qwait() The open routine sends down a T_INFO_REQ message and waits for the T_INFO_ACK. The arrival of the T_INFO_ACK is recorded by resetting a flag in the unit structure (WAIT_INFO_ACK). The example assumes that the module is D_MTQPAIR or D_MTPERMOD. xxopen(qp, ...) queue_t *qp; { struct xxdata *xx; /* Allocate xxdata structure */ qprocson(qp); /* Format T_INFO_ACK in mp */ putnext(qp, mp); xx->xx_flags |= WAIT_INFO_ACK; while (xx->xx_flags & WAIT_INFO_ACK) qwait(qp); return(0); } xxrput(qp, mp) queue_t *qp; mblk_t *mp; { struct xxdata *xx = (struct xxdata *)q->q_ptr; ... case T_INFO_ACK: if (xx->xx_flags & WAIT_INFO_ACK) { /* Record information from info ack */ xx->xx_flags &= ~WAIT_INFO_ACK; freemsg(mp); return; } ... } SEE ALSO
close(9E), open(9E), put(9E), srv(9E), condvar(9F), ddi_can_receive_sig(9F), mt-streams(9F), qbufcall(9F), qprocson(9F), qtimeout(9F) STREAMS Programming Guide Writing Device Drivers SunOS 5.10 15 Dec 2003 qwait(9F)

Featured Tech Videos