From 0dfbd93afe6e70cf203bbe05a6160b5b19e174a0 Mon Sep 17 00:00:00 2001
From: Ciro Santilli <ciro.santilli@gmail.com>
Date: Sun, 22 Jul 2018 19:54:56 +0100
Subject: [PATCH] failed sched_getaffinity_threads attempt

Better eigen naming.
---
 README.adoc                                   | 18 +++++++
 kernel_module/user/Makefile                   |  2 +-
 .../user/{eigen.cpp => eigen_hello.cpp}       |  0
 .../user/sched_getaffinity_threads.c          | 51 +++++++++++++++++++
 4 files changed, 70 insertions(+), 1 deletion(-)
 rename kernel_module/user/{eigen.cpp => eigen_hello.cpp} (100%)
 create mode 100644 kernel_module/user/sched_getaffinity_threads.c

diff --git a/README.adoc b/README.adoc
index c59a2d9..fe9c657 100644
--- a/README.adoc
+++ b/README.adoc
@@ -1997,6 +1997,24 @@ and we observe that `info threads` shows the actual correct core on which the pr
 
 We should also try it out with kernel modules: https://stackoverflow.com/questions/28347876/set-cpu-affinity-on-a-loadable-linux-kernel-module
 
+TODO we then tried:
+
+....
+./run -c2 -F '/sched_getaffinity_threads.out'
+....
+
+and:
+
+....
+./rungdb-user kernel_module-1.0/user/sched_getaffinity_threads.out
+....
+
+to switch between two simultaneous live threads with different affinities, it just didn't break on our threads:
+
+....
+b main_thread_0
+....
+
 Bibliography:
 
 * https://stackoverflow.com/questions/10490756/how-to-use-sched-getaffinity-and-sched-setaffinity-in-linux-from-c/50117787#50117787
diff --git a/kernel_module/user/Makefile b/kernel_module/user/Makefile
index a579057..4bd51c5 100644
--- a/kernel_module/user/Makefile
+++ b/kernel_module/user/Makefile
@@ -15,7 +15,7 @@ ifeq ($(BR2_PACKAGE_EIGEN),y)
 	# http://lists.busybox.net/pipermail/buildroot/2018-June/222914.html
 	#CXXFLAGS_EXTRA += $(shell $(PKG_CONFIG) --cflags eigen3)
 else
-	OUTS := $(filter-out eigen%$(OUT_EXT),$(OUTS))
+	OUTS := $(filter-out eigen_%$(OUT_EXT),$(OUTS))
 endif
 ifeq ($(BR2_PACKAGE_LIBDRM),y)
 	LIBS += $(shell $(PKG_CONFIG) --libs libdrm)
diff --git a/kernel_module/user/eigen.cpp b/kernel_module/user/eigen_hello.cpp
similarity index 100%
rename from kernel_module/user/eigen.cpp
rename to kernel_module/user/eigen_hello.cpp
diff --git a/kernel_module/user/sched_getaffinity_threads.c b/kernel_module/user/sched_getaffinity_threads.c
new file mode 100644
index 0000000..4e56996
--- /dev/null
+++ b/kernel_module/user/sched_getaffinity_threads.c
@@ -0,0 +1,51 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#gdb-step-debug-multicore */
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+void* main_thread_0(void *arg) {
+	int i;
+    cpu_set_t mask;
+    CPU_ZERO(&mask);
+    CPU_SET(*((int*)arg), &mask);
+    sched_setaffinity(0, sizeof(cpu_set_t), &mask);
+    i = 0;
+    while (true) {
+    	printf("0 %d\n", i);
+    	sleep(1);
+    	i++;
+    }
+    return NULL;
+}
+
+void* main_thread_1(void *arg) {
+	int i;
+    cpu_set_t mask;
+    CPU_ZERO(&mask);
+    CPU_SET(*((int*)arg), &mask);
+    sched_setaffinity(1, sizeof(cpu_set_t), &mask);
+    i = 0;
+    while (true) {
+    	printf("1 %d\n", i);
+    	sleep(1);
+    	i++;
+    }
+    return NULL;
+}
+
+int main(void) {
+    enum NUM_THREADS {NUM_THREADS = 2};
+    pthread_t threads[NUM_THREADS];
+    int thread_args[NUM_THREADS];
+	pthread_create(&threads[0], NULL, main_thread_0, (void*)&thread_args[0]);
+	pthread_create(&threads[1], NULL, main_thread_1, (void*)&thread_args[1]);
+    pthread_join(threads[0], NULL);
+    pthread_join(threads[1], NULL);
+    return EXIT_SUCCESS;
+}