Reset nice and ionice priorities when executing scripts.

Sometimes you may consider running an entire yum upgrade wrapped on nice and
ionice to soften the effect of the upcoming I/O and CPU storm on the system.
The side effect of that is that restarted services and anything else executed
from the pre- and post- rm and installation scripts will be niced and ioniced as
well, defeating the whole idea.

With this, you are safe to run it, because we will reset nice and ionice values
right after fork() to the defaults.

1 files changed, 30 insertions, 0 deletions

diff --git a/lib/rpmscript.c b/lib/rpmscript.c
index d8297b929..493f4f26a 100644
--- a/lib/rpmscript.c
+++ b/lib/rpmscript.c
@@ -4,6 +4,10 @@
 #include <sys/wait.h>
 #include <errno.h>
 #include <unistd.h>
+#include <sys/resource.h>
+#if defined(__linux__)
+#include <sys/syscall.h>        /* For ionice */
+#endif
 
 #include <rpm/rpmfileutil.h>
 #include <rpm/rpmmacro.h>
@@ -326,6 +330,32 @@ static rpmRC runExtScript(rpmPlugins plugins, ARGV_const_t prefixes,
 	fclose(in);
 	dup2(inpipe[0], STDIN_FILENO);
 
+        /* If RPM was invoked with nice and/or ionice, the scripts that we run
+         * will be also nice'd/ionice'd.  This is terrible if you restart any
+         * daemon (e.g. mysqld), so let's reset this to default values before
+         * taking any actions.
+         */
+
+        /* Call for resetting nice priority. */
+        int ret;
+        ret = setpriority(PRIO_PROCESS, 0, 0);
+        if (ret == -1) {
+            rpmlog(RPMLOG_WARNING, _("Unable to reset nice value: %s"),
+                strerror(errno));
+        }
+
+        /* Call for resetting IO priority. */
+        #if defined(__linux__)
+        /* Defined at include/linux/ioprio.h */
+        const int _IOPRIO_WHO_PROCESS = 1;
+        const int _IOPRIO_CLASS_NONE = 0;
+        ret = syscall(SYS_ioprio_set, _IOPRIO_WHO_PROCESS, 0, _IOPRIO_CLASS_NONE);
+        if (ret == -1) {
+            rpmlog(RPMLOG_WARNING, _("Unable to reset I/O priority: %s"),
+                strerror(errno));
+        }
+        #endif
+
 	/* Run scriptlet post fork hook for all plugins */
 	if (rpmpluginsCallScriptletForkPost(plugins, *argvp[0], RPMSCRIPTLET_FORK | RPMSCRIPTLET_EXEC) != RPMRC_FAIL) {
 	    doScriptExec(*argvp, prefixes, scriptFd, out);