+ hpfall-reduce-risk-that-hpfall-can-do-harm.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     hpfall: reduce risk that hpfall can do harm
has been added to the -mm tree.  Its filename is
     hpfall-reduce-risk-that-hpfall-can-do-harm.patch

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------------------------------------------------------
Subject: hpfall: reduce risk that hpfall can do harm
From: Christian Thaeter <ct@xxxxxxxxxx>

Improve the example code to be at least useable, as in not causing harm
(as shown below).  Code can still be improved further, but this adds some
basic safeguards.

1. hpfall *MUST* mlockall(MCL_CURRENT|MCL_FUTURE); itself!  Since the
   Program sits and waits most of the time it becomes very likely swapped
   out.  If it gets woken up when the laptop drops from the table while it
   is swapped out it actually triggers harddrive activity!

2. Daemonize hpfall using 'daemon(0,0)' (quick and dirty).

3. Give hpfall realtime priority.  Should give a chance that it has
   less latency when woken up.

Signed-off-by: Christian Thaeter <ct@xxxxxxxxxx>
Signed-off-by: Frans Pop <elendil@xxxxxxxxx>
Acked-by: Pavel Machek <pavel@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 Documentation/hwmon/hpfall.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff -puN Documentation/hwmon/hpfall.c~hpfall-reduce-risk-that-hpfall-can-do-harm Documentation/hwmon/hpfall.c
--- a/Documentation/hwmon/hpfall.c~hpfall-reduce-risk-that-hpfall-can-do-harm
+++ a/Documentation/hwmon/hpfall.c
@@ -16,6 +16,8 @@
 #include <stdint.h>
 #include <errno.h>
 #include <signal.h>
+#include <sys/mman.h>
+#include <sched.h>
 
 void write_int(char *path, int i)
 {
@@ -62,6 +64,7 @@ void ignore_me(void)
 int main(int argc, char *argv[])
 {
 	int fd, ret;
+	struct sched_param param;
 
 	fd = open("/dev/freefall", O_RDONLY);
 	if (fd < 0) {
@@ -69,6 +72,11 @@ int main(int argc, char *argv[])
 		return EXIT_FAILURE;
 	}
 
+	daemon(0, 0);
+	param.sched_priority = sched_get_priority_max(SCHED_FIFO);
+	sched_setscheduler(0, SCHED_FIFO, &param);
+	mlockall(MCL_CURRENT|MCL_FUTURE);
+
 	signal(SIGALRM, ignore_me);
 
 	for (;;) {
_

Patches currently in -mm which might be from ct@xxxxxxxxxx are

vm-document-that-setting-vfs_cache_pressure-to-0-isnt-a-good-idea.patch
hpfall-reduce-risk-that-hpfall-can-do-harm.patch
hpfall-accept-disk-device-to-unload-as-argument.patch

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