[erlang-questions] Yaws's "sendfile" linked-in driver : "stealing control of fd" error

zabrane Mikael zabrane3@REDACTED
Sun Apr 17 23:23:11 CEST 2011

Hi OTP team & Steve,

I'm using the "sendfile" (thanks to Steve Vinoski) linked-in driver
borrowed from "Yaws"
in one of my pet project.

Today, I noticed this strange error:
=ERROR REPORT==== 17-Apr-2011::20:49:18 ===
driver_select(0x0000000000000c31, 24, ERL_DRV_WRITE, 1) by
sendfile_drv driver #Port<0.3121> stealing control of fd=24 from
output driver tcp_inet #Port<0.10029>

Searching "stealing control of fd=" in the "otp_src_R14B02" source
code returns this:

otp_src_R14B02> find . -type "f" | xargs grep -n "stealing control of" | head -1

The C function printing out this error line is:
static void
steal(erts_dsprintf_buf_t *dsbufp, ErtsDrvEventState *state, int mode)
    erts_dsprintf(dsbufp, "stealing control of fd=%d from ", (int) state->fd);
    switch (state->type) {
    case ERTS_EV_TYPE_DRV_SEL: {
	int deselect_mode = 0;
	Eterm iid = state->driver.select->inport;
	Eterm oid = state->driver.select->outport;
	if ((mode & ERL_DRV_READ) && (is_not_nil(iid))) {
	    erts_dsprintf(dsbufp, "input driver ");
	    print_driver_name(dsbufp, iid);
	    erts_dsprintf(dsbufp, "%T ", iid);
	    deselect_mode |= ERL_DRV_READ;

Could someone please tell me what's the aim of this C function?
Should I consider this as an error or can I forget about it?


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