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timeout(9f) [sunos man page]

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

NAME
timeout - execute a function after a specified length of time SYNOPSIS
#include <sys/types.h> #include <sys/conf.h> timeout_id_t timeout(void (* func)(void *), void *arg, clock_t ticks); INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI). PARAMETERS
func Kernel function to invoke when the time increment expires. arg Argument to the function. ticks Number of clock ticks to wait before the function is called. Use drv_usectohz(9F) to convert microseconds to clock ticks. DESCRIPTION
The timeout() function schedules the specified function to be called after a specified time interval. The exact time interval over which the timeout takes effect cannot be guaranteed, but the value given is a close approximation. The function called by timeout() must adhere to the same restrictions as a driver soft interrupt handler. The delay(9F) function calls timeout(). Because timeout() is subject to priority inversion, drivers waiting on behalf of processes with real-time constraints should use cv_timedwait(9F) rather than delay(). RETURN VALUES
timeout() returns an opaque non-zero timeout identifier that can be passed to untimeout(9F) to cancel the request. CONTEXT
timeout() can be called from user or interrupt context. EXAMPLES
Example 1: Using timeout() In the following example, the device driver has issued an IO request and is waiting for the device to respond. If the device does not respond within 5 seconds, the device driver will print out an error message to the console. static void xxtimeout_handler(void *arg) { struct xxstate *xsp = (struct xxstate *)arg; mutex_enter(&xsp->lock); cv_signal(&xsp->cv); xsp->flags |= TIMED_OUT; mutex_exit(&xsp->lock); xsp->timeout_id = 0; } static uint_t xxintr(caddr_t arg) { struct xxstate *xsp = (struct xxstate *)arg; . . . mutex_enter(&xsp->lock); /* Service interrupt */ cv_signal(&xsp->cv); mutex_exit(&xsp->lock); if (xsp->timeout_id != 0) { (void) untimeout(xsp->timeout_id); xsp->timeout_id = 0; } return(DDI_INTR_CLAIMED); } static void xxcheckcond(struct xxstate *xsp) { . . . xsp->timeout_id = timeout(xxtimeout_handler, xsp, (5 * drv_usectohz(1000000))); mutex_enter(&xsp->lock); while (/* Waiting for interrupt or timeout*/) cv_wait(&xsp->cv, &xsp->lock); if (xsp->flags & TIMED_OUT) cmn_err(CE_WARN, "Device not responding"); . . . mutex_exit(&xsp->lock); . . . } SEE ALSO
bufcall(9F), cv_timedwait(9F), ddi_in_panic(9F), delay(9F), drv_usectohz(9F), untimeout(9F) Writing Device Drivers SunOS 5.10 15 Oct 2001 timeout(9F)

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

NAME
untimeout - cancel previous timeout function call SYNOPSIS
#include <sys/types.h> #include <sys/conf.h> clock_t untimeout(timeout_id_t id); INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI). PARAMETERS
id Opaque timeout ID from a previous timeout(9F) call. DESCRIPTION
The untimeout() function cancels a pending timeout(9F) request. untimeout() will not return until the pending callback is cancelled or has run. Because of this, locks acquired by the callback routine should not be held across the call to untimeout() or a deadlock may result. Since no mutex should be held across the call to untimeout(), there is a race condition between the occurrence of an expected event and the execution of the timeout handler. In particular, it should be noted that no problems will result from calling untimeout() for a timeout which is either running on another CPU, or has already completed. Drivers should be structured with the understanding that the arrival of both an interrupt and a timeout for that interrupt can occasionally occur, in either order. RETURN VALUES
The untimeout() function returns -1 if the id is not found. Otherwise, it returns an integer value greater than or equal to 0. CONTEXT
The untimeout() function can be called from user, interrupt, or kernel context. EXAMPLES
In the following example, the device driver has issued an IO request and is waiting for the device to respond. If the device does not respond within 5 seconds, the device driver will print out an error message to the console. static void xxtimeout_handler(void *arg) { struct xxstate *xsp = (struct xxstate *)arg; mutex_enter(&xsp->lock); cv_signal(&xsp->cv); xsp->flags |= TIMED_OUT; mutex_exit(&xsp->lock); xsp->timeout_id = 0; } static uint_t xxintr(caddr_t arg) { struct xxstate *xsp = (struct xxstate *)arg; . . . mutex_enter(&xsp->lock); /* Service interrupt */ cv_signal(&xsp->cv); mutex_exit(&xsp->lock); if (xsp->timeout_id != 0) { (void) untimeout(xsp->timeout_id); xsp->timeout_id = 0; } return(DDI_INTR_CLAIMED); } static void xxcheckcond(struct xxstate *xsp) { . . . xsp->timeout_id = timeout(xxtimeout_handler, xsp, (5 * drv_usectohz(1000000))); mutex_enter(&xsp->lock); while (/* Waiting for interrupt or timeout*/) cv_wait(&xsp->cv, &xsp->lock); if (xsp->flags & TIMED_OUT) cmn_err(CE_WARN, "Device not responding"); . . . mutex_exit(&xsp->lock); . . . } SEE ALSO
open(9E), cv_signal(9F), cv_wait_sig(9F), delay(9F), timeout(9F) Writing Device Drivers SunOS 5.11 16 Jan 2006 untimeout(9F)
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