Tests various percpu operations.
Enable with CONFIG_PERCPU_TEST=m.
Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
---
lib/Kconfig.debug | 9 ++++
lib/Makefile | 2 +
lib/percpu_test.c | 138 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 149 insertions(+)
create mode 100644 lib/percpu_test.c
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 06344d9..cee589d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1472,6 +1472,15 @@ config INTERVAL_TREE_TEST
help
A benchmark measuring the performance of the interval tree library
+config PERCPU_TEST
+ tristate "Per cpu counter test"
+ depends on m && DEBUG_KERNEL
+ help
+ Enable this option to build test modules with validates per-cpu
+ counter operations.
+
+ If unsure, say N.
+
config ATOMIC64_SELFTEST
bool "Perform an atomic64_t self-test at boot"
help
diff --git a/lib/Makefile b/lib/Makefile
index f3bb2cb..bb016e1 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -157,6 +157,8 @@ obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
interval_tree_test-objs := interval_tree_test_main.o interval_tree.o
+obj-$(CONFIG_PERCPU_TEST) += percpu_test.o
+
obj-$(CONFIG_ASN1) += asn1_decoder.o
obj-$(CONFIG_FONT_SUPPORT) += fonts/
diff --git a/lib/percpu_test.c b/lib/percpu_test.c
new file mode 100644
index 0000000..1ebeb44
--- /dev/null
+++ b/lib/percpu_test.c
@@ -0,0 +1,138 @@
+#include <linux/module.h>
+
+/* validate @native and @pcp counter values match @expected */
+#define CHECK(native, pcp, expected) \
+ do { \
+ WARN((native) != (expected), \
+ "raw %ld (0x%lx) != expected %ld (0x%lx)", \
+ (long)(native), (long)(native), \
+ (long)(expected), (long)(expected)); \
+ WARN(__this_cpu_read(pcp) != (expected), \
+ "pcp %ld (0x%lx) != expected %ld (0x%lx)", \
+ (long)__this_cpu_read(pcp), (long)__this_cpu_read(pcp), \
+ (long)(expected), (long)(expected)); \
+ } while (0)
+
+static DEFINE_PER_CPU(long, long_counter);
+static DEFINE_PER_CPU(unsigned long, ulong_counter);
+
+static int __init percpu_test_init(void)
+{
+ /*
+ * volatile prevents compiler from optimizing it uses, otherwise the
+ * +ul_one and -ul_one below would replace with inc/dec instructions.
+ */
+ volatile unsigned int ui_one = 1;
+ long l = 0;
+ unsigned long ul = 0;
+
+ pr_info("percpu test start\n");
+
+ preempt_disable();
+
+ l += -1;
+ __this_cpu_add(long_counter, -1);
+ CHECK(l, long_counter, -1);
+
+ l += 1;
+ __this_cpu_add(long_counter, 1);
+ CHECK(l, long_counter, 0);
+
+ ul = 0;
+ __this_cpu_write(ulong_counter, 0);
+
+ ul += 1UL;
+ __this_cpu_add(ulong_counter, 1UL);
+ CHECK(ul, ulong_counter, 1);
+
+ ul += -1UL;
+ __this_cpu_add(ulong_counter, -1UL);
+ CHECK(ul, ulong_counter, 0);
+
+ ul += -(unsigned long)1;
+ __this_cpu_add(ulong_counter, -(unsigned long)1);
+ CHECK(ul, ulong_counter, -1);
+
+ ul = 0;
+ __this_cpu_write(ulong_counter, 0);
+
+ ul -= 1;
+ __this_cpu_dec(ulong_counter);
+ CHECK(ul, ulong_counter, 0xffffffffffffffff);
+ CHECK(ul, ulong_counter, -1);
+
+ l += -ui_one;
+ __this_cpu_add(long_counter, -ui_one);
+ CHECK(l, long_counter, 0xffffffff);
+
+ l += ui_one;
+ __this_cpu_add(long_counter, ui_one);
+ CHECK(l, long_counter, 0x100000000);
+
+
+ l = 0;
+ __this_cpu_write(long_counter, 0);
+
+ l -= ui_one;
+ __this_cpu_sub(long_counter, ui_one);
+ CHECK(l, long_counter, -1);
+
+ l = 0;
+ __this_cpu_write(long_counter, 0);
+
+ l += ui_one;
+ __this_cpu_add(long_counter, ui_one);
+ CHECK(l, long_counter, 1);
+
+ l += -ui_one;
+ __this_cpu_add(long_counter, -ui_one);
+ CHECK(l, long_counter, 0x100000000);
+
+ l = 0;
+ __this_cpu_write(long_counter, 0);
+
+ l -= ui_one;
+ this_cpu_sub(long_counter, ui_one);
+ CHECK(l, long_counter, -1);
+ CHECK(l, long_counter, 0xffffffffffffffff);
+
+ ul = 0;
+ __this_cpu_write(ulong_counter, 0);
+
+ ul += ui_one;
+ __this_cpu_add(ulong_counter, ui_one);
+ CHECK(ul, ulong_counter, 1);
+
+ ul = 0;
+ __this_cpu_write(ulong_counter, 0);
+
+ ul -= ui_one;
+ __this_cpu_sub(ulong_counter, ui_one);
+ CHECK(ul, ulong_counter, -1);
+ CHECK(ul, ulong_counter, 0xffffffffffffffff);
+
+ ul = 3;
+ __this_cpu_write(ulong_counter, 3);
+
+ ul = this_cpu_sub_return(ulong_counter, ui_one);
+ CHECK(ul, ulong_counter, 2);
+
+ ul = __this_cpu_sub_return(ulong_counter, ui_one);
+ CHECK(ul, ulong_counter, 0);
+
+ preempt_enable();
+
+ pr_info("percpu test done\n");
+ return -EAGAIN; /* Fail will directly unload the module */
+}
+
+static void __exit percpu_test_exit(void)
+{
+}
+
+module_init(percpu_test_init)
+module_exit(percpu_test_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Greg Thelen");
+MODULE_DESCRIPTION("percpu variables test");
--
1.8.4.1
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