From 3f18cf0cfc3b79a9e1d4215c027955a9f5199104 Mon Sep 17 00:00:00 2001
From: Sean McBride <spmcbride1201@gmail.com>
Date: Mon, 26 Apr 2021 14:45:08 -0400
Subject: [PATCH] feat: make preemption toggle runtime config

---
 runtime/Makefile                 |  3 ---
 runtime/include/runtime.h        |  1 +
 runtime/src/main.c               |  8 ++++++++
 runtime/src/software_interrupt.c | 11 +++++------
 runtime/src/worker_thread.c      |  9 +++++----
 5 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/runtime/Makefile b/runtime/Makefile
index de58895..e69fce6 100644
--- a/runtime/Makefile
+++ b/runtime/Makefile
@@ -85,9 +85,6 @@ CFLAGS += -D${ARCH}
 CFLAGS += -DNCORES=${TOTAL_CORES}
 CFLAGS += -DPAGE_SIZE=$(PAGE_SIZE)
 
-# Optionally Disable preemption
-# CFLAGS += -DPREEMPT_DISABLE
-
 # Sandboxes running on Sledge always use WebAssembly linear memory
 CFLAGS += -DUSE_MEM_VM
 
diff --git a/runtime/include/runtime.h b/runtime/include/runtime.h
index b0266fa..83fc3b2 100644
--- a/runtime/include/runtime.h
+++ b/runtime/include/runtime.h
@@ -90,3 +90,4 @@ print_runtime_scheduler(enum RUNTIME_SCHEDULER variant)
 };
 
 extern enum RUNTIME_SCHEDULER runtime_scheduler;
+extern bool                   runtime_preemption_enabled;
diff --git a/runtime/src/main.c b/runtime/src/main.c
index 7411dd6..b9e7a97 100644
--- a/runtime/src/main.c
+++ b/runtime/src/main.c
@@ -40,6 +40,9 @@ FILE *runtime_sandbox_perf_log = NULL;
 enum RUNTIME_SCHEDULER runtime_scheduler = RUNTIME_SCHEDULER_FIFO;
 int                    runtime_worker_core_count;
 
+
+bool runtime_preemption_enabled = true;
+
 /**
  * Returns instructions on use of CLI if used incorrectly
  * @param cmd - The command the user entered
@@ -213,6 +216,11 @@ runtime_configure()
 	}
 	printf("\tScheduler Policy: %s\n", print_runtime_scheduler(runtime_scheduler));
 
+	/* Runtime Preemption Toggle */
+	char *preempt_disable = getenv("SLEDGE_DISABLE_PREEMPTION");
+	if (preempt_disable != NULL && strcmp(preempt_disable, "false") != 0) runtime_preemption_enabled = false;
+	printf("\tPreemption: %s\n", runtime_preemption_enabled ? "Enabled" : "Disabled");
+
 	/* Runtime Perf Log */
 	char *runtime_sandbox_perf_log_path = getenv("SLEDGE_SANDBOX_PERF_LOG");
 	if (runtime_sandbox_perf_log_path != NULL) {
diff --git a/runtime/src/software_interrupt.c b/runtime/src/software_interrupt.c
index c102044..8fce230 100644
--- a/runtime/src/software_interrupt.c
+++ b/runtime/src/software_interrupt.c
@@ -165,9 +165,9 @@ software_interrupt_validate_worker()
 static inline void
 software_interrupt_handle_signals(int signal_type, siginfo_t *signal_info, void *user_context_raw)
 {
-#ifdef PREEMPT_DISABLE
-	panic("Unexpectedly invoked signal handlers when PREEMPT_DISABLE set\n");
-#else
+	if (unlikely(!runtime_preemption_enabled)) {
+		panic("Unexpectedly invoked signal handlers with preemption disabled\n");
+	}
 
 	software_interrupt_validate_worker();
 
@@ -190,7 +190,6 @@ software_interrupt_handle_signals(int signal_type, siginfo_t *signal_info, void
 		}
 	}
 	}
-#endif
 }
 
 /********************
@@ -203,7 +202,8 @@ software_interrupt_handle_signals(int signal_type, siginfo_t *signal_info, void
 void
 software_interrupt_arm_timer(void)
 {
-#ifndef PREEMPT_DISABLE
+	if (!runtime_preemption_enabled) return;
+
 	struct itimerval interval_timer;
 
 	memset(&interval_timer, 0, sizeof(struct itimerval));
@@ -215,7 +215,6 @@ software_interrupt_arm_timer(void)
 		perror("setitimer");
 		exit(1);
 	}
-#endif
 }
 
 /**
diff --git a/runtime/src/worker_thread.c b/runtime/src/worker_thread.c
index 0250401..5e6fe7a 100644
--- a/runtime/src/worker_thread.c
+++ b/runtime/src/worker_thread.c
@@ -317,10 +317,11 @@ worker_thread_main(void *return_code)
 
 
 	/* Unmask signals */
-#ifndef PREEMPT_DISABLE
-	software_interrupt_unmask_signal(SIGALRM);
-	software_interrupt_unmask_signal(SIGUSR1);
-#endif
+	if (runtime_preemption_enabled) {
+		software_interrupt_unmask_signal(SIGALRM);
+		software_interrupt_unmask_signal(SIGUSR1);
+	}
+
 	signal(SIGPIPE, SIG_IGN);
 
 	/* Initialize epoll */