Bug#38477: my_pthread_setprio can change dispatch class on Solaris, not just priority

The problem is that the function used by the server to increase
the thread's priority (pthread_setschedparam) has the unintended
side-effect of changing the calling thread scheduling policy,
possibly overwriting a scheduling policy set by a sysadmin.

The solution is to rely on the pthread_setschedprio function, if
available, as it only changes the scheduling priority and does not
change the scheduling policy. This function is usually available on
Solaris and Linux, but it use won't work by default on Linux as the
the default scheduling policy only accepts a static priority 0 -- this
is acceptable for now as priority changing on Linux is broken anyway.

configure.in:
  Check for the existence of the pthread_setschedprio function.
include/my_pthread.h:
  Use the pthread_setschedprio function to set the thread priority
  if the function is available.

1 files changed, 2 insertions, 0 deletions

diff --git a/include/my_pthread.h b/include/my_pthread.h
index e56614357e0..151cb34faff 100644
--- a/include/my_pthread.h
+++ b/include/my_pthread.h
@@ -279,6 +279,8 @@ int sigwait(sigset_t *setp, int *sigp);		/* Use our implemention */
 #define my_pthread_setprio(A,B) pthread_setprio_np((A),(B))
 #elif defined(HAVE_PTHREAD_SETPRIO)
 #define my_pthread_setprio(A,B) pthread_setprio((A),(B))
+#elif defined(HAVE_PTHREAD_SETSCHEDPRIO)
+#define my_pthread_setprio(A,B) pthread_setschedprio((A),(B))
 #else
 extern void my_pthread_setprio(pthread_t thread_id,int prior);
 #endif