sleep_on

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
AVAILABILITY
SEE ALSO
AUTHOR
BUGS

NAME

sleep_on − synchronization using a condition variable

SYNOPSIS

#include

DESCRIPTION

The sleep_on function provides a means for synchronizing between processes and with interrupt handlers. The condition parameter is a pointer to a pointer to the opaque wait_queue type. Initialize the condition variable to zero, then pass a pointer to it to the sleep_on function. The basic idea is as follows:

struct wait_queue*con = 0;

sleep_on(&con);

While a process is sleeping, it is fully interruptible, no matter what the cpu state when entering the function. The cpu state is restored on being awakened.

If a null(0) is passed to sleep_on, it returns immediately, without sleeping. This is a no-op.

RETURN VALUE

The sleep_on function only returns when explicitly awakened.

AVAILABILITY

Linux 1+

SEE ALSO

wake_up(9)

/usr/src/linux/kernel/sched.c

AUTHOR

Stephen Williams

BUGS

A call to sleep_on(0) seems like an interesting way to test for and momentarily allow interrupts, but that is not what happens.

The sleep_on function cannot be called by interrupt handlers.

The function is not atomic with the condition tests that the driver writer might include, so the code executing the sleep_on function is protected from interrupts. Failure to do so generally leads to race conditions.