While browsing through the source of pm-utils, I noticed that the
lock/unlocking functions were using file creation/removal and PID
checking for locking purposes. In a shell scripting language,
however, there is no way to atomically create files.
Directory creation, however, is atomic. Here is a patch to atomicize
the lock/unlick functions.
diff -ur -X diffignore pm-utils/pm/functions working/pm/functions
--- pm-utils/pm/functions 2007-12-29 05:58:18.000000000 -0600
+++ working/pm/functions 2008-01-04 14:52:18.000000000 -0600
@@ -40,13 +40,9 @@
{
VT=$(fgconsole)
chvt 63
- if [ -f /.suspended ]; then
- read pid < /.suspended
- if [ -d /proc/$pid ]; then
- return 1
- fi
- fi
- echo "$$" > /.suspended
+ # file creation and reading is not atomic.
+ # Directory creation is.
+ mkdir /.suspended || return 1
rm -f /var/run/pm-suspend
touch /var/run/pm-suspend
return 0
@@ -57,7 +53,7 @@
rm -f /var/run/pm-suspend
chvt 1
chvt $VT
- openvt -- sh -c "usleep $1 ; rm -f /.suspended >/dev/null 2>&1 0<&1" >/dev/null 2>&1 0<&1 &
+ openvt -- sh -c "usleep $1 ; rm -rf /.suspended >/dev/null 2>&1 0<&1" >/dev/null 2>&1 0<&1 &
}
find_sleepd_files()
diff -ur -X diffignore pm-utils/src/pm/functions working/src/pm/functions
--- pm-utils/src/pm/functions 2007-12-29 05:58:18.000000000 -0600
+++ working/src/pm/functions 2008-01-04 14:53:41.000000000 -0600
@@ -40,13 +40,9 @@
{
VT=$(fgconsole)
chvt 63
- if [ -f /.suspended ]; then
- read pid < /.suspended
- if [ -d /proc/$pid ]; then
- return 1
- fi
- fi
- echo "$$" > /.suspended
+ # file creation and reading is not atomic.
+ # Directory creation is.
+ mkdir /.suspended || return 1
rm -f /var/run/pm-suspend
touch /var/run/pm-suspend
return 0
@@ -57,7 +53,7 @@
rm -f /var/run/pm-suspend
chvt 1
chvt $VT
- openvt -- sh -c "usleep $1 ; rm -f /.suspended >/dev/null 2>&1 0<&1" >/dev/null 2>&1 0<&1 &
+ openvt -- sh -c "usleep $1 ; rm -rf /.suspended >/dev/null 2>&1 0<&1" >/dev/null 2>&1 0<&1 &
}
find_sleepd_files()
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