Kernel-provided semaphore

C semaphore interface, see L4::Semaphore for the C++ interface. More...

Collaboration diagram for Kernel-provided semaphore:

Functions
l4_msgtag_t	l4_semaphore_up (l4_cap_idx_t sem) L4_NOTHROW
	Semaphore up operation (wrapper for trigger()).
l4_msgtag_t	l4_semaphore_down (l4_cap_idx_t sem, l4_timeout_t timeout) L4_NOTHROW
	Semaphore down operation.

Detailed Description

C semaphore interface, see L4::Semaphore for the C++ interface.

Include File

#include <l4/sys/semaphore.h> 

Function Documentation

l4_semaphore_down()

l4_msgtag_t l4_semaphore_down ( l4_cap_idx_t  sem, l4_timeout_t  timeout  )

inline

Semaphore down operation.

Parameters

sem	Semaphore object.
timeout	Timeout for blocking the semaphore down operation. Note: The receive timeout of this timeout-pair is significant for blocking, the send part is usually non-blocking.

Returns

Syscall return tag. Use l4_error() to check for errors.

Return values

-L4_EPERM

No L4_CAP_FPAGE_S right on invoked semaphore capability.

This method decrements the semaphore counter by one, or blocks if the counter is already zero, until either a timeout or cancel condition hits or the counter is increased by an up() operation.

Definition at line 110 of file semaphore.h.

References l4_utcb().

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l4_semaphore_up()

l4_msgtag_t l4_semaphore_up ( l4_cap_idx_t  sem )

inline

Semaphore up operation (wrapper for trigger()).

Parameters

sem	Semaphore object.

Returns

Send-only IPC message return tag. Use l4_ipc_error() to check for errors, do not use l4_error().

Increases the semaphore counter by one if it is smaller than an unspecified limit. The unspecified limit is guaranteed to be at least 2^31-1.

Definition at line 56 of file semaphore.h.

References l4_irq_trigger().

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