untimeout(9F)

NAME

untimeout − cancel previous timeout(9F) function call

SYNOPSIS

#include <sys/types.h>
int untimeout(int id);

ARGUMENTS

id Identification value generated by a previous timeout(9F) function call.

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

DESCRIPTION

untimeout() cancels a pending timeout(9F) request.

RETURN VALUES

untimeout() returns -1 if the id is not found or the slot index otherwise.

CONTEXT

untimeout() can be called from user or interrupt context.

EXAMPLE

A driver may have to repeatedly request outside help from a computer operator. The timeout function is used to delay a certain amount of time between requests. However, once the request is honored, the driver will want to cancel the timeout operation. This is done with the untimeout function.

In a driver open(9E) routine, after the input arguments have been verified, the status of the device is tested. If the device is not on-line, a message is displayed on the system console. The driver schedules a wakeup() call and waits for five minutes (line 41). If the device is still not ready, the procedure is repeated.

When the device is made ready, an interrupt is generated. The driver interrupt handling routine notes there is a suspended process. It cancels the timeout request (line 59) and wakens the suspended process (line 61).

1 struct mtu_device {
2/∗ layout of physical device registers ∗/
3          int      control;/∗ physical device control word ∗/
4          int      status;/∗ physical device status word ∗/
5          int      byte_cnt;/∗ number of bytes to be transferred ∗/
6          paddr_t baddr:/∗ DMA starting physical address ∗/
7 };/∗ end device ∗/
8
9 struct mtu     {
10/∗ magnetic tape unit logical structure ∗/
11         struct buf ∗mtu_head;/∗ pointer to I/O queue head ∗/
12         struct buf ∗mtu_tail;/∗ pointer to buffer I/O queue tail ∗/
13         int         mtu_flag;/∗ logical status flag ∗/
14         int         mtu_to_id;/∗ time out ID number ∗/
             ...
15 };/∗ end mtu ∗/
16
17 extern struct mtu_device ∗mtu_addr[]; /∗ location of dev regs ∗/
18 extern struct mtu         mtu_tbl[];/∗ location of dev structs ∗/
19 extern int    mtu_cnt;
      ...
20 mtu_open(dev, flag, type, c_ptr)
21      dev_t dev;
22 {
23      register struct mtu ∗dp;
24      register struct mtu_device ∗rp;
25      if ((getminor(dev) >> 3) > mtu_cnt) { /∗ if dev doesn’t exist ∗/
26          return(ENXIO);/∗ then return error condition ∗/
27      }/∗ endif ∗/
28
29      dp = &mtu_tbl[getminor(dev)];/∗ get logical device struct ∗/
30      if (dp->mtu_flag & MTU_BUSY) != 0) { /∗ if device is in use, ∗/
31          return(EBUSY);/∗ return busy status ∗/
32      }/∗ endif ∗/
33
34      dp->mtu_flag = MTU_BUSY;/∗ mark device in use & clear flags ∗/
35      rp = xx_addr[getminor(dev) >> 3]; /∗ get device regs ∗/
36      oldlevel2 = splhi();
37      while((rp->status & MTU_LOAD) == 0) { /∗ while tape not loaded ∗/
38/∗ display mount request on console ∗/
39          cmn_err(CE_NOTE, "!Tape MOUNT, drive %d", minor(dev) & 0x3);
40          dp->mtu_flag |= MTU_WAIT; /∗ indicate process suspended ∗/
41          dp->mtu_to_id = timeout(wakeup, dp, 5∗60∗HZ); /∗ wait 5 min ∗/
42          if (sleep(dp, (PCATCH | PZERO+2)) == 1){ /∗ wait on tape load ∗/
43/∗ if user aborts process, release ∗/
44              dp->mtu_flag = 0;/∗ tape device by clearing flags ∗/
45              untimeout(dp->mtu_to_id);
46              splx(oldlevel2);
47           }/∗ endif ∗/
48      }/∗ endwhile ∗/
49      splx(oldlevel2);
50 }/∗ end mtu_open ∗/
       ...
51 mtu_int(cntr)
52      int cntr;/∗ controller that caused the interrupt ∗/
53 {
54 register struct mtu_device ∗rp = xx_addr[cntr]; /∗ get device regs ∗/
55 register struct mtu ∗dp = &mtu_tbl[cntr << 3 | (rp->status & 0x3)];
       ...
56     if ((dp->mtu_flag & MTU_WAIT) != 0){ /∗ if process is suspended ∗/
57/∗ waiting for tape mount, ∗/
58          untimeout(dp->mtu_to_id);/∗ cancel timeout request ∗/
59          dp->flag &= ~MTU_WAIT;/∗ clear wait flag ∗/
60          wakeup(dp);/∗ awaken suspended process ∗/
61     }/∗ endif ∗/
       ...

Museum

Related Articles