Add support for RT patches (#380)

* Add support for RT patches

* Disallow other CPU schedulers on PREEMPT_RT

customization.cfg

@@ -104,6 +104,16 @@ _llvm_ias=""
 # "thin: uses multiple threads, faster and uses less memory, may have a lower runtime performance than Full."
 _lto_mode=""
 
+# Apply PREEMPT_RT patchset to the kernel.
+# ! Only CFS CPU scheduler is compatible with this patchset !
+# Set to "1" to enable.
+_preempt_rt=""
+
+# Forcibly apply the PREEMPT_RT patchset to the kernel, even when upstream does not officially support the kernel subversion.
+# ! This will still not apply when the patch itself or linux-tkg (see _version) do not support the kernel major version - Not recommended !
+# Set to "1" to enable.
+_preempt_rt_force=""
+
 # CPU sched_yield_type - Choose what sort of yield sched_yield will perform
 # For PDS and MuQSS: 0: No yield. (Recommended option for gaming on PDS and MuQSS)
 #                    1: Yield only to better priority/deadline tasks. (Default - can be unstable with PDS on some platforms)

install.sh

@@ -314,7 +314,11 @@ if [ "$1" = "install" ]; then
   fi
 
   if [ -z $_kernel_localversion ]; then
-    _kernel_flavor="tkg-${_cpusched}${_compiler_name}"
+    if [ "$_preempt_rt" = "1" ]; then
+      _kernel_flavor="tkg-${_cpusched}-rt${_compiler_name}"
+    else
+      _kernel_flavor="tkg-${_cpusched}${_compiler_name}"
+    fi
   else
     _kernel_flavor="tkg-${_kernel_localversion}"
   fi

linux-tkg-config/prepare

@@ -3,7 +3,7 @@
 # Needed for prompting with the correct order
 _supported_kernels=("5.16" "5.15" "5.14" "5.13" "5.12" "5.11" "5.10" "5.9" "5.8" "5.7" "5.4")
 
-typeset -A _kver_subver_map
+typeset -Ag _kver_subver_map
 _kver_subver_map=(
   ["5.4"]="164"
   ["5.7"]="19"
@@ -18,6 +18,29 @@ _kver_subver_map=(
   ["5.16"]="rc4"
 )
 
+# PREEMPT_RT's supported kernel subversion
+typeset -Ag _rt_subver_map
+_rt_subver_map=(
+  ["5.4"]="161"
+  ["5.9"]="1"
+  ["5.10"]="83"
+  ["5.11"]="4"
+  ["5.14"]="2"
+  ["5.15"]="5"
+)
+
+# PREEMPT_RT's patch revision for the kernel
+# We separated this to allow for forcing the application of the patch when _preempt_rt_force=1 on version mismatch
+typeset -Ag _rt_rev_map
+_rt_rev_map=(
+  ["5.4"]="66"
+  ["5.9"]="20"
+  ["5.10"]="58"
+  ["5.11"]="11"
+  ["5.14"]="21"
+  ["5.15"]="22"
+)
+
 _undefine() {
   for _config_name in "$@"; do
     scripts/config -k --undefine "${_config_name}"
@@ -141,6 +164,10 @@ _set_cpu_scheduler() {
     _avail_cpu_scheds=("cfs")
   fi
 
+  if [ "${_preempt_rt}" = "1" ]; then
+    _avail_cpu_scheds=("cfs")
+  fi
+
   # Populate descriptions of the available CPU schedulers
   _avail_cpu_scheds_text=()
   for _sched in "${_avail_cpu_scheds[@]}"; do
@@ -393,6 +420,29 @@ _tkg_srcprep() {
   fi
   _msg="Applying graysky's cpu opts patch (legacy)" && _tkg_patcher
 
+  # PREEMPT_RT patch
+  if [ "${_preempt_rt}" = "1" ]; then
+    if [ ${_rt_subver_map[$_basekernel]+_} = "_" ]; then
+      preempt_rt_ksubver="${_rt_subver_map[$_basekernel]}"
+      # Check if subversion is supported, skip check if forced
+      if [ "${_preempt_rt_force}" = "1" ] || [ "${preempt_rt_ksubver}" = "${_kver_subver_map[$_basekernel]}" ]; then
+        preempt_rt_file_gz="patch-${_basekernel}.${preempt_rt_ksubver}-rt${_rt_rev_map["$_basekernel"]}.patch.gz"
+        preempt_rt_file=`basename ${preempt_rt_file_gz} .gz`
+        wget -P "$srcdir" "https://cdn.kernel.org/pub/linux/kernel/projects/rt/${_basekernel}/${preempt_rt_file_gz}"
+        last_pwd=`pwd`
+        cd "$srcdir"
+        gunzip -k "$srcdir/${preempt_rt_file_gz}"
+        cd "$last_pwd"
+        tkgpatch="$srcdir/${preempt_rt_file}"
+        _msg="Applying PREEMPT_RT patch" && _tkg_patcher
+      else
+        msg2 "Skipping PREEMPT_RT patch for ${_basekernel}.${_sub}"
+      fi
+    else
+      msg2 "Skipping PREEMPT_RT patch on unsupported kernel version"
+    fi
+  fi
+
   # TkG
   tkgpatch="$srcdir/0002-clear-patches.patch"
   _msg="Applying clear linux patches" && _tkg_patcher