MsgError(), MsgError

Unblock a client and set its errno

Synopsis:

#include <sys/neutrino.h>

int MsgError( int rcvid,
              int error );

int MsgError_r( int rcvid,
                int error );

Arguments:

rcvid: The receive ID that MsgReceive*() returned.
error: The error code that you want to set for the client.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The MsgError() and MsgError_r() kernel calls unblock the client's MsgSend*() call and set the client's errno to error. No data is transferred.

If error is EOK, the MsgSend*() call returns EOK; if error is any other value, the MsgSend*() call returns -1.

These functions are identical except in the way they indicate errors. See the Returns section for details.

Note: An error number of ERESTART causes the sender to immediately call MsgSend*() again. Since send and reply buffers passed to MsgSend() may overlap, you shouldn't use ERESTART after a call to MsgWrite().

Blocking states

None for the local case. In the network case:

STATE_REPLY: The calling thread is waiting for a network operation to complete. The calling thread is marked as REPLY-blocked on itself (the same process ID as the thread making the call).

Native networking

MsgError() has increased latency when you use it to communicate across a network—the server is now writing the error code to its local lsm-qnet.so, which may need to communicate with the client's lsm-qnet.so to actually transfer the error code.

Returns:

The only difference between these functions is the way they indicate errors:

MsgError(): If an error occurs, the function returns -1 and sets errno. Any other value returned indicates success.
MsgError_r(): Returns EOK on success. This function does NOT set errno. If an error occurs, the function returns one of the values listed in the Errors section.

Errors:

ESRCH: The thread indicated by rcvid doesn't exist.
ETIMEDOUT: A kernel timeout unblocked the call. See TimerTimeout().

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes

MsgError(), MsgError_r()