ASYNC IO using RT Signals

ASYNC IO using RT Signals

[Bharath Ramesh]

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A question on sigwaitinfo based IO mechanism in multithreaded
applications.

I am trying to use RT signals to notify me of IO events using RT signals
instead of SIGIO in a multithreaded applications. I noticed that there
was some discussion on lkml during november 1999 with the subject of the
discussion as "Signal driven IO". In the thread I noticed that RT
signals were being delivered to the worker thread. I am running 2.6.10
kernel and I am trying to use the very same mechanism and I find that
only SIGIO being propogated to the worker threads and RT signals only
being propogated to the main thread and not the worker threads where I
actually want them to be propogated too. On further inspection I found
that the following patch which I have attached solves the problem.

I am not sure if this is a bug or feature in the kernel.

Thanks,

Bharath

---
Bharath Ramesh       <bramesh@vt.edu>       http://csgrad.cs.vt.edu/~bramesh


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--- linux-2.6.10/fs/fcntl.c.orig	2004-12-24 16:35:01.000000000 -0500
+++ linux-2.6.10/fs/fcntl.c	2005-03-22 14:30:14.298415152 -0500
@@ -469,7 +469,7 @@ static void send_sigio_to_task(struct ta
 			else
 				si.si_band = band_table[reason - POLL_IN];
 			si.si_fd    = fd;
-			if (!send_sig_info(fown->signum, &si, p))
+			if (!send_group_sig_info(fown->signum, &si, p))
 				break;
 		/* fall-through: fall back on the old plain SIGIO signal */
 		case 0: