ipc_send (nr 506)

Send a message on an IPC channel (blocking).

Signature

ipc_send(fd: i32, msg_ptr: *const IpcMessage, flags: u32) → 0 or -errno

Arguments

Arg	Register	Description
fd	rdi	Channel send-end fd (from `ipc_create`)
msg_ptr	rsi	Pointer to `IpcMessage` to send
flags	rdx	`IPC_NONBLOCK` (0x1) for non-blocking mode

Errors

Error	Condition
EFAULT	`msg_ptr` is invalid
EBADF	`fd` is not a valid channel send-end
EPIPE	Receive end has been closed
EAGAIN	`IPC_NONBLOCK` set and channel is full
EMFILE	(receiver) fd table full during fd transfer

Description

Sends a message through the channel. If the channel buffer is full and IPC_NONBLOCK is not set, the calling thread blocks until the receiver drains space.

If msg.fds contains valid file descriptors (not -1), those fd objects are extracted from the sender’s fd table and transferred to the receiver. The sender’s fds remain open — this is a dup, not a move.

When a receiver is blocked waiting via ipc_recv, the send uses scheduler donate to directly switch to the receiver thread for low-latency delivery.

For async (non-blocking, multiplexed) sending, use OP_IPC_SEND via io_submit instead.

Implementation

osl/src/ipc.rs — sys_ipc_send

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