Kernel: Set priority of all threads within a process if requested

This is intended to reflect the POSIX sched_setparam API, which has some
cryptic language
(https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_08_04_01
) that as far as I can tell implies we should prioritize process
scheduling policies over thread scheduling policies. Technically this
means that a process must have its own sets of policies that are
considered first by the scheduler, but it seems unlikely anyone relies
on this behavior in practice. So we just override all thread's policies,
making them (at least before calls to pthread_setschedparam) behave
exactly like specified on the surface.

1 files changed, 8 insertions, 1 deletions

diff --git a/Kernel/Syscalls/sched.cpp b/Kernel/Syscalls/sched.cpp
index a9351bb27b..f5db4eadbf 100644
--- a/Kernel/Syscalls/sched.cpp
+++ b/Kernel/Syscalls/sched.cpp
@@ -75,8 +75,15 @@ ErrorOr<FlatPtr> Process::sys$scheduler_set_parameters(Userspace<Syscall::SC_sch
     if (!credentials->is_superuser() && credentials->euid() != peer_credentials->uid() && credentials->uid() != peer_credentials->uid())
         return EPERM;
 
-    // FIXME: Only sets priority for main thread of process if mode == PROCESS
     peer->set_priority((u32)parameters.parameters.sched_priority);
+    // POSIX says that process scheduling parameters have precedence over thread scheduling parameters.
+    // We don't track them separately, so overwrite the thread scheduling settings manually for now.
+    if (parameters.mode == Syscall::SchedulerParametersMode::Process) {
+        peer->process().for_each_thread([&](auto& thread) {
+            thread.set_priority((u32)parameters.parameters.sched_priority);
+        });
+    }
+
     return 0;
 }