DCMD_CHR_WAITINFO

Get information about blocked processes

Synopsis:

#include <sys/dcmd_chr.h>

#define DCMD_CHR_WAITINFO   __DIOTF(_DCMD_CHR, 11, struct _ttywaitinfo)

Arguments to devctl():

Argument	Value
`filedes`	A file descriptor that you obtained by opening the device.
`dcmd`	DCMD_CHR_WAITINFO
`dev_data_ptr`	A pointer to a struct _ttywaitinfo
`n_bytes`	`sizeof(struct _ttywaitinfo)` (see below)
`dev_info_ptr`	NULL

Description:

This command gets information about blocked processes. The client passes in the queue to query and the number of blocked processes that it can handle seeing.

The associated data types are:

typedef enum _tty_queue {
        TTY_NULL_Q,
        TTY_DEVCTL_Q,
        TTY_DRAIN_Q,
        TTY_WRITE_Q,
        TTY_READ_Q,
        TTY_OPEN_Q     /* By definition we won't see see anything here,
                          since we have to open the device to query it */
} _ttyqueue;

struct _pidtid {
        pid_t pid;
        int   tid;
        int   offset;
        int   nbytes;
};

struct _ttywaitinfo {
        _ttyqueue      queue;
        unsigned int   num;
        struct _pidtid blocked[0];
};

Input:

A _ttywaitinfo structure, with:

queue set to the desired _tty_queue value
num set to the number of entries in the blocked array
enough space to hold the blocked array

Output:

A _ttywaitinfo structure, with the blocked array filled in, and num set to the number of entries that were filled in.

Errors:

The devctl() function can return the following, in addition to the error codes listed in its entry in the C Library Reference:

ENOTTY: You specified an invalid queue.