From: Ian Jackson <ian@davenant.greenend.org.uk>
Date: Sun, 9 Jan 2011 19:07:40 +0000 (+0000)
Subject: hostside: do serial irq priority poking with a helper script and a pipe in /var/run... 
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ijackson/git?a=commitdiff_plain;ds=sidebyside;h=a45c35ae9738b166beb04588161da5a2b2cdaa11;p=trains.git

hostside: do serial irq priority poking with a helper script and a pipe in /var/run, yuck
---

diff --git a/hostside/realtime.c b/hostside/realtime.c
index 46f6c06..44b01ed 100644
--- a/hostside/realtime.c
+++ b/hostside/realtime.c
@@ -376,6 +376,25 @@ void check_rusage_check(int always_report) {
   }
 }
 
+#define SERINTRPOKE "/var/run/serial-irq-priority-poke"
+
+static void serial_interrupt_priority(void) {
+  int fd= open(SERINTRPOKE, O_WRONLY|O_NONBLOCK);
+  if (fd<0) {
+    if (errno==ENOENT || errno==EAGAIN || errno==EACCES || errno==EWOULDBLOCK)
+      return;
+    diee("failed to open " SERINTRPOKE);
+  }
+  static char dummy;
+  int r= write(fd,&dummy,1);
+  if (r!=1) {
+    assert(r<0);
+    if (!(errno==EWOULDBLOCK))
+      diee("failed to write a byte to " SERINTRPOKE);
+  }
+  close(fd);
+}
+
 /*---------- debugging ----------*/
 
 unsigned long eventcounter;
@@ -565,6 +584,7 @@ int main(int argc, const char **argv) {
     if (nononblock_stdin) oop_fd_nonblock(0,0);
 
     serial_open(device);
+    serial_interrupt_priority();
     r= oop_fd_nonblock(serial_fd, 1);  if (r) diee("nonblock(serial_fd,1)");
 
     events->on_fd(events, serial_fd, OOP_READ, serial_readable, 0);
diff --git a/hostside/serial-irq-priority b/hostside/serial-irq-priority
index aee45b4..3b3350b 100755
--- a/hostside/serial-irq-priority
+++ b/hostside/serial-irq-priority
@@ -1,15 +1,22 @@
 #!/bin/bash
 set -ex
-exec 4</dev/railway
 
-ssd=`start-stop-daemon --stop -t -u root -n irq/4-serial`
-case "$ssd" in
-"Would send signal 15 to "*.) ;;
-*) echo >&2 "start-stop-daemon said $ssd ?"; exit 1;;
-esac
-pid="${ssd##* }"
-pid="${pid%.}"
+cd /var/run
+p=serial-irq-priority-poke
+rm -f $p
+mkfifo -m 622 $p
+exec 3<>$p
 
-echo chrt -p 55 $pid
+while read -n 1 <&3 dummy; do
 
-exec sleep 1000000000
+	ssd=`start-stop-daemon --stop -t -u root -n irq/4-serial`
+	case "$ssd" in
+	"Would send signal 15 to "*.)
+		pid="${ssd##* }"
+		pid="${pid%.}"
+		chrt -p 55 $pid ||:
+		;;
+	*) echo >&2 "start-stop-daemon said $ssd ?"; continue;;
+	esac
+
+done