RELEASE_CONSOLE_SEM(9) Driver Basics RELEASE_CONSOLE_SEM(9)NAME
release_console_sem - unlock the console system
SYNOPSIS
void release_console_sem(void);
ARGUMENTS
void
no arguments
DESCRIPTION
Releases the semaphore which the caller holds on the console system and the console driver list.
While the semaphore was held, console output may have been buffered by printk. If this is the case, release_console_sem emits the output
prior to releasing the semaphore.
If there is output waiting for klogd, we wake it up.
release_console_sem may be called from any context.
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 RELEASE_CONSOLE_SEM(9)
Check Out this Related Man Page
sem_post(3) Library Functions Manual sem_post(3)NAME
sem_post - Unlocks a semaphore (P1003.1b)
LIBRARY
Realtime Library (librt.so, librt.a)
SYNOPSIS
#include <semaphore.h>
int sem_post (
sem_t *sem);
PARAMETERS
sem Pointer to the semaphore to be unlocked.
DESCRIPTION
The sem_post function unlocks the specified semaphore by performing the semaphore unlock operation on that semaphore. The appropriate func-
tion (sem_open for named semaphores or sem_init for unnamed semaphores) must be called for a semaphore before you can call the locking and
unlocking functions, sem_wait, sem_trywait, and sem_post.
If the semaphore value after a sem_post function is positive, no processes were blocked waiting for the semaphore to be unlocked; the sema-
phore value is incremented. If the semaphore value after a sem_post function is zero, one of the processes blocked waiting for the sema-
phore is allowed to return successfully from its call to sem_wait.
If more than one process is blocked while waiting for the semaphore, only one process is unblocked and the state of the semaphore remains
unchanged when the sem_post function returns. The process to be unblocked is selected according to the scheduling policies and priorities
of all blocked processes. If the scheduling policy is SCHED_FIFO or SCHED_RR, the highest-priority waiting process is unblocked. If more
than one process of that priority is blocked, then the process that has waited the longest is unblocked.
The sem_post function can be called from a signal-catching function.
RETURN VALUES
On successful completion, the sem_post function returns the value 0 (zero) and performs a semaphore unlock operation, unblocking a process.
Otherwise, the function returns the value -1 and sets errno to indicate the error. The state of the semaphore remains unchanged.
ERRORS
The sem_post function fails under the following condition:
[EINVAL] The sem does not refer to a valid semaphore.
RELATED INFORMATION
Functions: sem_trywait(3), sem_wait(3)
Guide to Realtime Programming delim off
sem_post(3)
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