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Message-Id: <1469135662-31512-8-git-send-email-mathieu.desnoyers@efficios.com>
Date: Thu, 21 Jul 2016 17:14:22 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Russell King <linux@....linux.org.uk>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
Paul Turner <pjt@...gle.com>, Andrew Hunter <ahh@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Andy Lutomirski <luto@...capital.net>,
Andi Kleen <andi@...stfloor.org>,
Dave Watson <davejwatson@...com>, Chris Lameter <cl@...ux.com>,
Ben Maurer <bmaurer@...com>,
Steven Rostedt <rostedt@...dmis.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Josh Triplett <josh@...htriplett.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Michael Kerrisk <mtk.manpages@...il.com>,
Boqun Feng <boqun.feng@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH v7 7/7] Restartable sequences: self-tests
Implements two basic tests of RSEQ functionality, and one more
exhaustive parameterizable test.
The first, "basic_test" only asserts that RSEQ works moderately
correctly.
E.g. that:
- The CPUID pointer works
- Code infinitely looping within a critical section will eventually be
interrupted.
- Critical sections are interrupted by signals.
"basic_percpu_ops_test" is a slightly more "realistic" variant,
implementing a few simple per-cpu operations and testing their
correctness.
"param_test" is a parametrizable restartable sequences test. See
the "--help" output for usage.
As part of those tests, a helper library "rseq" implements a user-space
API around restartable sequences. It takes care of ensuring progress in
case of debugger single-stepping with a fall-back to locking, and
exposes the instruction pointer addresses where the rseq assembly blocks
begin and end, as well as the associated abort instruction pointer, in
the __rseq_table section. This section allows debuggers may know where
to place breakpoints when single-stepping through assembly blocks which
may be aborted at any point by the kernel.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC: Russell King <linux@....linux.org.uk>
CC: Catalin Marinas <catalin.marinas@....com>
CC: Will Deacon <will.deacon@....com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Paul Turner <pjt@...gle.com>
CC: Andrew Hunter <ahh@...gle.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Andy Lutomirski <luto@...capital.net>
CC: Andi Kleen <andi@...stfloor.org>
CC: Dave Watson <davejwatson@...com>
CC: Chris Lameter <cl@...ux.com>
CC: Ingo Molnar <mingo@...hat.com>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Ben Maurer <bmaurer@...com>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
CC: Josh Triplett <josh@...htriplett.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: Boqun Feng <boqun.feng@...il.com>
CC: linux-api@...r.kernel.org
---
tools/testing/selftests/rseq/.gitignore | 3 +
tools/testing/selftests/rseq/Makefile | 13 +
.../testing/selftests/rseq/basic_percpu_ops_test.c | 279 ++++++++
tools/testing/selftests/rseq/basic_test.c | 106 +++
tools/testing/selftests/rseq/param_test.c | 707 +++++++++++++++++++++
tools/testing/selftests/rseq/rseq.c | 200 ++++++
tools/testing/selftests/rseq/rseq.h | 449 +++++++++++++
7 files changed, 1757 insertions(+)
create mode 100644 tools/testing/selftests/rseq/.gitignore
create mode 100644 tools/testing/selftests/rseq/Makefile
create mode 100644 tools/testing/selftests/rseq/basic_percpu_ops_test.c
create mode 100644 tools/testing/selftests/rseq/basic_test.c
create mode 100644 tools/testing/selftests/rseq/param_test.c
create mode 100644 tools/testing/selftests/rseq/rseq.c
create mode 100644 tools/testing/selftests/rseq/rseq.h
diff --git a/tools/testing/selftests/rseq/.gitignore b/tools/testing/selftests/rseq/.gitignore
new file mode 100644
index 0000000..2596e26
--- /dev/null
+++ b/tools/testing/selftests/rseq/.gitignore
@@ -0,0 +1,3 @@
+basic_percpu_ops_test
+basic_test
+param_test
diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
new file mode 100644
index 0000000..3d1ad8e
--- /dev/null
+++ b/tools/testing/selftests/rseq/Makefile
@@ -0,0 +1,13 @@
+CFLAGS += -O2 -Wall -g -I../../../../usr/include/
+LDFLAGS += -lpthread
+
+TESTS = basic_test basic_percpu_ops_test param_test
+
+all: $(TESTS)
+%: %.c rseq.h rseq.c
+ $(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+
+include ../lib.mk
+
+clean:
+ $(RM) $(TESTS)
diff --git a/tools/testing/selftests/rseq/basic_percpu_ops_test.c b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
new file mode 100644
index 0000000..4667dc5
--- /dev/null
+++ b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
@@ -0,0 +1,279 @@
+#define _GNU_SOURCE
+#include <assert.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "rseq.h"
+
+static struct rseq_lock rseq_lock;
+
+struct percpu_lock_entry {
+ intptr_t v;
+} __attribute__((aligned(128)));
+
+struct percpu_lock {
+ struct percpu_lock_entry c[CPU_SETSIZE];
+};
+
+struct test_data_entry {
+ int count;
+} __attribute__((aligned(128)));
+
+struct spinlock_test_data {
+ struct percpu_lock lock;
+ struct test_data_entry c[CPU_SETSIZE];
+ int reps;
+};
+
+struct percpu_list_node {
+ intptr_t data;
+ struct percpu_list_node *next;
+};
+
+struct percpu_list_entry {
+ struct percpu_list_node *head;
+} __attribute__((aligned(128)));
+
+struct percpu_list {
+ struct percpu_list_entry c[CPU_SETSIZE];
+};
+
+/* A simple percpu spinlock. Returns the cpu lock was acquired on. */
+int rseq_percpu_lock(struct percpu_lock *lock)
+{
+ struct rseq_state rseq_state;
+ intptr_t *targetptr, newval;
+ int cpu;
+ bool result;
+
+ for (;;) {
+ do_rseq(&rseq_lock, rseq_state, cpu, result, targetptr, newval,
+ {
+ if (unlikely(lock->c[cpu].v)) {
+ result = false;
+ } else {
+ newval = 1;
+ targetptr = (intptr_t *)&lock->c[cpu].v;
+ }
+ });
+ if (likely(result))
+ break;
+ }
+ /*
+ * Acquire semantic when taking lock after control dependency.
+ * Matches smp_store_release().
+ */
+ smp_acquire__after_ctrl_dep();
+ return cpu;
+}
+
+void rseq_percpu_unlock(struct percpu_lock *lock, int cpu)
+{
+ assert(lock->c[cpu].v == 1);
+ /*
+ * Release lock, with release semantic. Matches
+ * smp_acquire__after_ctrl_dep().
+ */
+ smp_store_release(&lock->c[cpu].v, 0);
+}
+
+void *test_percpu_spinlock_thread(void *arg)
+{
+ struct spinlock_test_data *data = arg;
+ int i, cpu;
+
+ if (rseq_init_current_thread())
+ abort();
+ for (i = 0; i < data->reps; i++) {
+ cpu = rseq_percpu_lock(&data->lock);
+ data->c[cpu].count++;
+ rseq_percpu_unlock(&data->lock, cpu);
+ }
+
+ return NULL;
+}
+
+/*
+ * A simple test which implements a sharded counter using a per-cpu
+ * lock. Obviously real applications might prefer to simply use a
+ * per-cpu increment; however, this is reasonable for a test and the
+ * lock can be extended to synchronize more complicated operations.
+ */
+void test_percpu_spinlock(void)
+{
+ const int num_threads = 200;
+ int i, sum;
+ pthread_t test_threads[num_threads];
+ struct spinlock_test_data data;
+
+ memset(&data, 0, sizeof(data));
+ data.reps = 5000;
+
+ for (i = 0; i < num_threads; i++)
+ pthread_create(&test_threads[i], NULL,
+ test_percpu_spinlock_thread, &data);
+
+ for (i = 0; i < num_threads; i++)
+ pthread_join(test_threads[i], NULL);
+
+ sum = 0;
+ for (i = 0; i < CPU_SETSIZE; i++)
+ sum += data.c[i].count;
+
+ assert(sum == data.reps * num_threads);
+}
+
+int percpu_list_push(struct percpu_list *list, struct percpu_list_node *node)
+{
+ struct rseq_state rseq_state;
+ intptr_t *targetptr, newval;
+ int cpu;
+ bool result;
+
+ do_rseq(&rseq_lock, rseq_state, cpu, result, targetptr, newval,
+ {
+ newval = (intptr_t)node;
+ targetptr = (intptr_t *)&list->c[cpu].head;
+ node->next = list->c[cpu].head;
+ });
+
+ return cpu;
+}
+
+/*
+ * Unlike a traditional lock-less linked list; the availability of a
+ * rseq primitive allows us to implement pop without concerns over
+ * ABA-type races.
+ */
+struct percpu_list_node *percpu_list_pop(struct percpu_list *list)
+{
+ struct percpu_list_node *head, *next;
+ struct rseq_state rseq_state;
+ intptr_t *targetptr, newval;
+ int cpu;
+ bool result;
+
+ do_rseq(&rseq_lock, rseq_state, cpu, result, targetptr, newval,
+ {
+ head = list->c[cpu].head;
+ if (!head) {
+ result = false;
+ } else {
+ next = head->next;
+ newval = (intptr_t) next;
+ targetptr = (intptr_t *)&list->c[cpu].head;
+ }
+ });
+
+ return head;
+}
+
+void *test_percpu_list_thread(void *arg)
+{
+ int i;
+ struct percpu_list *list = (struct percpu_list *)arg;
+
+ if (rseq_init_current_thread())
+ abort();
+
+ for (i = 0; i < 100000; i++) {
+ struct percpu_list_node *node = percpu_list_pop(list);
+
+ sched_yield(); /* encourage shuffling */
+ if (node)
+ percpu_list_push(list, node);
+ }
+
+ return NULL;
+}
+
+/* Simultaneous modification to a per-cpu linked list from many threads. */
+void test_percpu_list(void)
+{
+ int i, j;
+ long sum = 0, expected_sum = 0;
+ struct percpu_list list;
+ pthread_t test_threads[200];
+ cpu_set_t allowed_cpus;
+
+ memset(&list, 0, sizeof(list));
+
+ /* Generate list entries for every usable cpu. */
+ sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus);
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ if (!CPU_ISSET(i, &allowed_cpus))
+ continue;
+ for (j = 1; j <= 100; j++) {
+ struct percpu_list_node *node;
+
+ expected_sum += j;
+
+ node = malloc(sizeof(*node));
+ assert(node);
+ node->data = j;
+ node->next = list.c[i].head;
+ list.c[i].head = node;
+ }
+ }
+
+ for (i = 0; i < 200; i++)
+ assert(pthread_create(&test_threads[i], NULL,
+ test_percpu_list_thread, &list) == 0);
+
+ for (i = 0; i < 200; i++)
+ pthread_join(test_threads[i], NULL);
+
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ cpu_set_t pin_mask;
+ struct percpu_list_node *node;
+
+ if (!CPU_ISSET(i, &allowed_cpus))
+ continue;
+
+ CPU_ZERO(&pin_mask);
+ CPU_SET(i, &pin_mask);
+ sched_setaffinity(0, sizeof(pin_mask), &pin_mask);
+
+ while ((node = percpu_list_pop(&list))) {
+ sum += node->data;
+ free(node);
+ }
+ }
+
+ /*
+ * All entries should now be accounted for (unless some external
+ * actor is interfering with our allowed affinity while this
+ * test is running).
+ */
+ assert(sum == expected_sum);
+}
+
+int main(int argc, char **argv)
+{
+ if (rseq_init_lock(&rseq_lock)) {
+ perror("rseq_init_lock");
+ return -1;
+ }
+ if (rseq_init_current_thread())
+ goto error;
+ printf("spinlock\n");
+ test_percpu_spinlock();
+ printf("percpu_list\n");
+ test_percpu_list();
+
+ if (rseq_destroy_lock(&rseq_lock)) {
+ perror("rseq_destroy_lock");
+ return -1;
+ }
+ return 0;
+
+error:
+ if (rseq_destroy_lock(&rseq_lock))
+ perror("rseq_destroy_lock");
+ return -1;
+}
+
diff --git a/tools/testing/selftests/rseq/basic_test.c b/tools/testing/selftests/rseq/basic_test.c
new file mode 100644
index 0000000..e8fdcd6
--- /dev/null
+++ b/tools/testing/selftests/rseq/basic_test.c
@@ -0,0 +1,106 @@
+/*
+ * Basic test coverage for critical regions and rseq_current_cpu().
+ */
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/time.h>
+
+#include "rseq.h"
+
+volatile int signals_delivered;
+volatile __thread struct rseq_state sigtest_start;
+static struct rseq_lock rseq_lock;
+
+void test_cpu_pointer(void)
+{
+ cpu_set_t affinity, test_affinity;
+ int i;
+
+ sched_getaffinity(0, sizeof(affinity), &affinity);
+ CPU_ZERO(&test_affinity);
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ if (CPU_ISSET(i, &affinity)) {
+ CPU_SET(i, &test_affinity);
+ sched_setaffinity(0, sizeof(test_affinity),
+ &test_affinity);
+ assert(rseq_current_cpu() == sched_getcpu());
+ assert(rseq_current_cpu() == i);
+ CPU_CLR(i, &test_affinity);
+ }
+ }
+ sched_setaffinity(0, sizeof(affinity), &affinity);
+}
+
+/*
+ * This depends solely on some environmental event triggering a counter
+ * increase.
+ */
+void test_critical_section(void)
+{
+ struct rseq_state start;
+ uint32_t event_counter;
+
+ start = rseq_start(&rseq_lock);
+ event_counter = start.event_counter;
+ do {
+ start = rseq_start(&rseq_lock);
+ } while (start.event_counter == event_counter);
+}
+
+void test_signal_interrupt_handler(int signo)
+{
+ struct rseq_state current;
+
+ current = rseq_start(&rseq_lock);
+ /*
+ * The potential critical section bordered by 'start' must be
+ * invalid.
+ */
+ assert(current.event_counter != sigtest_start.event_counter);
+ signals_delivered++;
+}
+
+void test_signal_interrupts(void)
+{
+ struct itimerval it = { { 0, 1 }, { 0, 1 } };
+
+ setitimer(ITIMER_PROF, &it, NULL);
+ signal(SIGPROF, test_signal_interrupt_handler);
+
+ do {
+ sigtest_start = rseq_start(&rseq_lock);
+ } while (signals_delivered < 10);
+ setitimer(ITIMER_PROF, NULL, NULL);
+}
+
+int main(int argc, char **argv)
+{
+ if (rseq_init_lock(&rseq_lock)) {
+ perror("rseq_init_lock");
+ return -1;
+ }
+ if (rseq_init_current_thread())
+ goto init_thread_error;
+ printf("testing current cpu\n");
+ test_cpu_pointer();
+ printf("testing critical section\n");
+ test_critical_section();
+ printf("testing critical section is interrupted by signal\n");
+ test_signal_interrupts();
+
+ if (rseq_destroy_lock(&rseq_lock)) {
+ perror("rseq_destroy_lock");
+ return -1;
+ }
+ return 0;
+
+init_thread_error:
+ if (rseq_destroy_lock(&rseq_lock))
+ perror("rseq_destroy_lock");
+ return -1;
+}
diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c
new file mode 100644
index 0000000..f95fba5
--- /dev/null
+++ b/tools/testing/selftests/rseq/param_test.c
@@ -0,0 +1,707 @@
+#define _GNU_SOURCE
+#include <assert.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <unistd.h>
+#include <poll.h>
+#include <sys/types.h>
+#include <signal.h>
+#include <errno.h>
+
+static inline pid_t gettid(void)
+{
+ return syscall(__NR_gettid);
+}
+
+#define NR_INJECT 9
+static int loop_cnt[NR_INJECT + 1];
+
+static int opt_modulo;
+
+static int opt_yield, opt_signal, opt_sleep, opt_fallback_cnt = 3,
+ opt_disable_rseq, opt_threads = 200,
+ opt_reps = 5000, opt_disable_mod = 0, opt_test = 's';
+
+static __thread unsigned int signals_delivered;
+
+static struct rseq_lock rseq_lock;
+
+#ifndef BENCHMARK
+
+static __thread unsigned int yield_mod_cnt, nr_retry;
+
+#define printf_nobench(fmt, ...) printf(fmt, ## __VA_ARGS__)
+
+#define RSEQ_INJECT_INPUT \
+ , [loop_cnt_1]"m"(loop_cnt[1]) \
+ , [loop_cnt_2]"m"(loop_cnt[2]) \
+ , [loop_cnt_3]"m"(loop_cnt[3]) \
+ , [loop_cnt_4]"m"(loop_cnt[4])
+
+#if defined(__x86_64__) || defined(__i386__)
+
+#define INJECT_ASM_REG "eax"
+
+#define RSEQ_INJECT_CLOBBER \
+ , INJECT_ASM_REG
+
+#define RSEQ_INJECT_ASM(n) \
+ "mov %[loop_cnt_" #n "], %%" INJECT_ASM_REG "\n\t" \
+ "test %%" INJECT_ASM_REG ",%%" INJECT_ASM_REG "\n\t" \
+ "jz 333f\n\t" \
+ "222:\n\t" \
+ "dec %%" INJECT_ASM_REG "\n\t" \
+ "jnz 222b\n\t" \
+ "333:\n\t"
+
+#elif defined(__ARMEL__)
+
+#define INJECT_ASM_REG "r4"
+
+#define RSEQ_INJECT_CLOBBER \
+ , INJECT_ASM_REG
+
+#define RSEQ_INJECT_ASM(n) \
+ "ldr " INJECT_ASM_REG ", %[loop_cnt_" #n "]\n\t" \
+ "cmp " INJECT_ASM_REG ", #0\n\t" \
+ "beq 333f\n\t" \
+ "222:\n\t" \
+ "subs " INJECT_ASM_REG ", #1\n\t" \
+ "bne 222b\n\t" \
+ "333:\n\t"
+
+#else
+#error unsupported target
+#endif
+
+#define RSEQ_INJECT_FAILED \
+ nr_retry++;
+
+#define RSEQ_INJECT_C(n) \
+{ \
+ int loc_i, loc_nr_loops = loop_cnt[n]; \
+ \
+ for (loc_i = 0; loc_i < loc_nr_loops; loc_i++) { \
+ barrier(); \
+ } \
+ if (loc_nr_loops == -1 && opt_modulo) { \
+ if (yield_mod_cnt == opt_modulo - 1) { \
+ if (opt_sleep > 0) \
+ poll(NULL, 0, opt_sleep); \
+ if (opt_yield) \
+ sched_yield(); \
+ if (opt_signal) \
+ raise(SIGUSR1); \
+ yield_mod_cnt = 0; \
+ } else { \
+ yield_mod_cnt++; \
+ } \
+ } \
+}
+
+#define RSEQ_FALLBACK_CNT \
+ opt_fallback_cnt
+
+#else
+
+#define printf_nobench(fmt, ...)
+
+#endif /* BENCHMARK */
+
+#include "rseq.h"
+
+struct percpu_lock_entry {
+ intptr_t v;
+} __attribute__((aligned(128)));
+
+struct percpu_lock {
+ struct percpu_lock_entry c[CPU_SETSIZE];
+};
+
+struct test_data_entry {
+ int count;
+} __attribute__((aligned(128)));
+
+struct spinlock_test_data {
+ struct percpu_lock lock;
+ struct test_data_entry c[CPU_SETSIZE];
+};
+
+struct spinlock_thread_test_data {
+ struct spinlock_test_data *data;
+ int reps;
+ int reg;
+};
+
+struct inc_test_data {
+ struct test_data_entry c[CPU_SETSIZE];
+};
+
+struct inc_thread_test_data {
+ struct inc_test_data *data;
+ int reps;
+ int reg;
+};
+
+struct percpu_list_node {
+ intptr_t data;
+ struct percpu_list_node *next;
+};
+
+struct percpu_list_entry {
+ struct percpu_list_node *head;
+} __attribute__((aligned(128)));
+
+struct percpu_list {
+ struct percpu_list_entry c[CPU_SETSIZE];
+};
+
+/* A simple percpu spinlock. Returns the cpu lock was acquired on. */
+static int rseq_percpu_lock(struct percpu_lock *lock)
+{
+ struct rseq_state rseq_state;
+ intptr_t *targetptr, newval;
+ int cpu;
+ bool result;
+
+ for (;;) {
+ do_rseq(&rseq_lock, rseq_state, cpu, result, targetptr, newval,
+ {
+ if (unlikely(lock->c[cpu].v)) {
+ result = false;
+ } else {
+ newval = 1;
+ targetptr = (intptr_t *)&lock->c[cpu].v;
+ }
+ });
+ if (likely(result))
+ break;
+ }
+ /*
+ * Acquire semantic when taking lock after control dependency.
+ * Matches smp_store_release().
+ */
+ smp_acquire__after_ctrl_dep();
+ return cpu;
+}
+
+static void rseq_percpu_unlock(struct percpu_lock *lock, int cpu)
+{
+ assert(lock->c[cpu].v == 1);
+ /*
+ * Release lock, with release semantic. Matches
+ * smp_acquire__after_ctrl_dep().
+ */
+ smp_store_release(&lock->c[cpu].v, 0);
+}
+
+void *test_percpu_spinlock_thread(void *arg)
+{
+ struct spinlock_thread_test_data *thread_data = arg;
+ struct spinlock_test_data *data = thread_data->data;
+ int i, cpu;
+
+ if (!opt_disable_rseq && thread_data->reg
+ && rseq_init_current_thread())
+ abort();
+ for (i = 0; i < thread_data->reps; i++) {
+ cpu = rseq_percpu_lock(&data->lock);
+ data->c[cpu].count++;
+ rseq_percpu_unlock(&data->lock, cpu);
+#ifndef BENCHMARK
+ if (i != 0 && !(i % (thread_data->reps / 10)))
+ printf("tid %d: count %d\n", (int) gettid(), i);
+#endif
+ }
+ printf_nobench("tid %d: number of retry: %d, signals delivered: %u, nr_fallback %u, nr_fallback_wait %u\n",
+ (int) gettid(), nr_retry, signals_delivered,
+ __rseq_thread_state.fallback_cnt,
+ __rseq_thread_state.fallback_wait_cnt);
+ return NULL;
+}
+
+/*
+ * A simple test which implements a sharded counter using a per-cpu
+ * lock. Obviously real applications might prefer to simply use a
+ * per-cpu increment; however, this is reasonable for a test and the
+ * lock can be extended to synchronize more complicated operations.
+ */
+void test_percpu_spinlock(void)
+{
+ const int num_threads = opt_threads;
+ int i, sum, ret;
+ pthread_t test_threads[num_threads];
+ struct spinlock_test_data data;
+ struct spinlock_thread_test_data thread_data[num_threads];
+
+ memset(&data, 0, sizeof(data));
+ for (i = 0; i < num_threads; i++) {
+ thread_data[i].reps = opt_reps;
+ if (opt_disable_mod <= 0 || (i % opt_disable_mod))
+ thread_data[i].reg = 1;
+ else
+ thread_data[i].reg = 0;
+ thread_data[i].data = &data;
+ ret = pthread_create(&test_threads[i], NULL,
+ test_percpu_spinlock_thread, &thread_data[i]);
+ if (ret) {
+ errno = ret;
+ perror("pthread_create");
+ abort();
+ }
+ }
+
+ for (i = 0; i < num_threads; i++) {
+ pthread_join(test_threads[i], NULL);
+ if (ret) {
+ errno = ret;
+ perror("pthread_join");
+ abort();
+ }
+ }
+
+ sum = 0;
+ for (i = 0; i < CPU_SETSIZE; i++)
+ sum += data.c[i].count;
+
+ assert(sum == opt_reps * num_threads);
+}
+
+void *test_percpu_inc_thread(void *arg)
+{
+ struct inc_thread_test_data *thread_data = arg;
+ struct inc_test_data *data = thread_data->data;
+ int i;
+
+ if (!opt_disable_rseq && thread_data->reg
+ && rseq_init_current_thread())
+ abort();
+ for (i = 0; i < thread_data->reps; i++) {
+ struct rseq_state rseq_state;
+ intptr_t *targetptr, newval;
+ int cpu;
+ bool result;
+
+ do_rseq(&rseq_lock, rseq_state, cpu, result, targetptr, newval,
+ {
+ newval = (intptr_t)data->c[cpu].count + 1;
+ targetptr = (intptr_t *)&data->c[cpu].count;
+ });
+
+#ifndef BENCHMARK
+ if (i != 0 && !(i % (thread_data->reps / 10)))
+ printf("tid %d: count %d\n", (int) gettid(), i);
+#endif
+ }
+ printf_nobench("tid %d: number of retry: %d, signals delivered: %u, nr_fallback %u, nr_fallback_wait %u\n",
+ (int) gettid(), nr_retry, signals_delivered,
+ __rseq_thread_state.fallback_cnt,
+ __rseq_thread_state.fallback_wait_cnt);
+ return NULL;
+}
+
+void test_percpu_inc(void)
+{
+ const int num_threads = opt_threads;
+ int i, sum, ret;
+ pthread_t test_threads[num_threads];
+ struct inc_test_data data;
+ struct inc_thread_test_data thread_data[num_threads];
+
+ memset(&data, 0, sizeof(data));
+ for (i = 0; i < num_threads; i++) {
+ thread_data[i].reps = opt_reps;
+ if (opt_disable_mod <= 0 || (i % opt_disable_mod))
+ thread_data[i].reg = 1;
+ else
+ thread_data[i].reg = 0;
+ thread_data[i].data = &data;
+ ret = pthread_create(&test_threads[i], NULL,
+ test_percpu_inc_thread, &thread_data[i]);
+ if (ret) {
+ errno = ret;
+ perror("pthread_create");
+ abort();
+ }
+ }
+
+ for (i = 0; i < num_threads; i++) {
+ pthread_join(test_threads[i], NULL);
+ if (ret) {
+ errno = ret;
+ perror("pthread_join");
+ abort();
+ }
+ }
+
+ sum = 0;
+ for (i = 0; i < CPU_SETSIZE; i++)
+ sum += data.c[i].count;
+
+ assert(sum == opt_reps * num_threads);
+}
+
+int percpu_list_push(struct percpu_list *list, struct percpu_list_node *node)
+{
+ struct rseq_state rseq_state;
+ intptr_t *targetptr, newval;
+ int cpu;
+ bool result;
+
+ do_rseq(&rseq_lock, rseq_state, cpu, result, targetptr, newval,
+ {
+ newval = (intptr_t)node;
+ targetptr = (intptr_t *)&list->c[cpu].head;
+ node->next = list->c[cpu].head;
+ });
+
+ return cpu;
+}
+
+/*
+ * Unlike a traditional lock-less linked list; the availability of a
+ * rseq primitive allows us to implement pop without concerns over
+ * ABA-type races.
+ */
+struct percpu_list_node *percpu_list_pop(struct percpu_list *list)
+{
+ struct percpu_list_node *head, *next;
+ struct rseq_state rseq_state;
+ intptr_t *targetptr, newval;
+ int cpu;
+ bool result;
+
+ do_rseq(&rseq_lock, rseq_state, cpu, result, targetptr, newval,
+ {
+ head = list->c[cpu].head;
+ if (!head) {
+ result = false;
+ } else {
+ next = head->next;
+ newval = (intptr_t) next;
+ targetptr = (intptr_t *) &list->c[cpu].head;
+ }
+ });
+
+ return head;
+}
+
+void *test_percpu_list_thread(void *arg)
+{
+ int i;
+ struct percpu_list *list = (struct percpu_list *)arg;
+
+ if (rseq_init_current_thread())
+ abort();
+
+ for (i = 0; i < opt_reps; i++) {
+ struct percpu_list_node *node = percpu_list_pop(list);
+
+ if (opt_yield)
+ sched_yield(); /* encourage shuffling */
+ if (node)
+ percpu_list_push(list, node);
+ }
+
+ return NULL;
+}
+
+/* Simultaneous modification to a per-cpu linked list from many threads. */
+void test_percpu_list(void)
+{
+ const int num_threads = opt_threads;
+ int i, j, ret;
+ long sum = 0, expected_sum = 0;
+ struct percpu_list list;
+ pthread_t test_threads[num_threads];
+ cpu_set_t allowed_cpus;
+
+ memset(&list, 0, sizeof(list));
+
+ /* Generate list entries for every usable cpu. */
+ sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus);
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ if (!CPU_ISSET(i, &allowed_cpus))
+ continue;
+ for (j = 1; j <= 100; j++) {
+ struct percpu_list_node *node;
+
+ expected_sum += j;
+
+ node = malloc(sizeof(*node));
+ assert(node);
+ node->data = j;
+ node->next = list.c[i].head;
+ list.c[i].head = node;
+ }
+ }
+
+ for (i = 0; i < num_threads; i++) {
+ ret = pthread_create(&test_threads[i], NULL,
+ test_percpu_list_thread, &list);
+ if (ret) {
+ errno = ret;
+ perror("pthread_create");
+ abort();
+ }
+ }
+
+ for (i = 0; i < num_threads; i++) {
+ pthread_join(test_threads[i], NULL);
+ if (ret) {
+ errno = ret;
+ perror("pthread_join");
+ abort();
+ }
+ }
+
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ cpu_set_t pin_mask;
+ struct percpu_list_node *node;
+
+ if (!CPU_ISSET(i, &allowed_cpus))
+ continue;
+
+ CPU_ZERO(&pin_mask);
+ CPU_SET(i, &pin_mask);
+ sched_setaffinity(0, sizeof(pin_mask), &pin_mask);
+
+ while ((node = percpu_list_pop(&list))) {
+ sum += node->data;
+ free(node);
+ }
+ }
+
+ /*
+ * All entries should now be accounted for (unless some external
+ * actor is interfering with our allowed affinity while this
+ * test is running).
+ */
+ assert(sum == expected_sum);
+}
+
+static void test_signal_interrupt_handler(int signo)
+{
+ signals_delivered++;
+}
+
+static int set_signal_handler(void)
+{
+ int ret = 0;
+ struct sigaction sa;
+ sigset_t sigset;
+
+ ret = sigemptyset(&sigset);
+ if (ret < 0) {
+ perror("sigemptyset");
+ return ret;
+ }
+
+ sa.sa_handler = test_signal_interrupt_handler;
+ sa.sa_mask = sigset;
+ sa.sa_flags = 0;
+ ret = sigaction(SIGUSR1, &sa, NULL);
+ if (ret < 0) {
+ perror("sigaction");
+ return ret;
+ }
+
+ printf_nobench("Signal handler set for SIGUSR1\n");
+
+ return ret;
+}
+
+static void show_usage(int argc, char **argv)
+{
+ printf("Usage : %s <OPTIONS>\n",
+ argv[0]);
+ printf("OPTIONS:\n");
+ printf(" [-1 loops] Number of loops for delay injection 1\n");
+ printf(" [-2 loops] Number of loops for delay injection 2\n");
+ printf(" [-3 loops] Number of loops for delay injection 3\n");
+ printf(" [-4 loops] Number of loops for delay injection 4\n");
+ printf(" [-5 loops] Number of loops for delay injection 5 (-1 to enable -m)\n");
+ printf(" [-6 loops] Number of loops for delay injection 6 (-1 to enable -m)\n");
+ printf(" [-7 loops] Number of loops for delay injection 7 (-1 to enable -m)\n");
+ printf(" [-8 loops] Number of loops for delay injection 8 (-1 to enable -m)\n");
+ printf(" [-9 loops] Number of loops for delay injection 9 (-1 to enable -m)\n");
+ printf(" [-m N] Yield/sleep/kill every modulo N (default 0: disabled) (>= 0)\n");
+ printf(" [-y] Yield\n");
+ printf(" [-k] Kill thread with signal\n");
+ printf(" [-s S] S: =0: disabled (default), >0: sleep time (ms)\n");
+ printf(" [-f N] Use fallback every N failure (>= 1)\n");
+ printf(" [-t N] Number of threads (default 200)\n");
+ printf(" [-r N] Number of repetitions per thread (default 5000)\n");
+ printf(" [-d] Disable rseq system call (no initialization)\n");
+ printf(" [-D M] Disable rseq for each M threads\n");
+ printf(" [-T test] Choose test: (s)pinlock, (l)ist, (i)ncrement\n");
+ printf(" [-h] Show this help.\n");
+ printf("\n");
+}
+
+int main(int argc, char **argv)
+{
+ int i;
+
+ if (rseq_init_lock(&rseq_lock)) {
+ perror("rseq_init_lock");
+ return -1;
+ }
+ if (set_signal_handler())
+ goto error;
+ for (i = 1; i < argc; i++) {
+ if (argv[i][0] != '-')
+ continue;
+ switch (argv[i][1]) {
+ case '1':
+ case '2':
+ case '3':
+ case '4':
+ case '5':
+ case '6':
+ case '7':
+ case '8':
+ case '9':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ loop_cnt[argv[i][1] - '0'] = atol(argv[i + 1]);
+ i++;
+ break;
+ case 'm':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ opt_modulo = atol(argv[i + 1]);
+ if (opt_modulo < 0) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ i++;
+ break;
+ case 's':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ opt_sleep = atol(argv[i + 1]);
+ if (opt_sleep < 0) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ i++;
+ break;
+ case 'y':
+ opt_yield = 1;
+ break;
+ case 'k':
+ opt_signal = 1;
+ break;
+ case 'd':
+ opt_disable_rseq = 1;
+ break;
+ case 'D':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ opt_disable_mod = atol(argv[i + 1]);
+ if (opt_disable_mod < 0) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ i++;
+ break;
+ case 'f':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ opt_fallback_cnt = atol(argv[i + 1]);
+ if (opt_fallback_cnt < 1) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ i++;
+ break;
+ case 't':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ opt_threads = atol(argv[i + 1]);
+ if (opt_threads < 0) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ i++;
+ break;
+ case 'r':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ opt_reps = atol(argv[i + 1]);
+ if (opt_reps < 0) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ i++;
+ break;
+ case 'h':
+ show_usage(argc, argv);
+ goto end;
+ case 'T':
+ if (argc < i + 2) {
+ show_usage(argc, argv);
+ goto error;
+ }
+ opt_test = *argv[i + 1];
+ switch (opt_test) {
+ case 's':
+ case 'l':
+ case 'i':
+ break;
+ default:
+ show_usage(argc, argv);
+ goto error;
+ }
+ i++;
+ break;
+ default:
+ show_usage(argc, argv);
+ goto error;
+ }
+ }
+
+ if (!opt_disable_rseq && rseq_init_current_thread())
+ goto error;
+ switch (opt_test) {
+ case 's':
+ printf_nobench("spinlock\n");
+ test_percpu_spinlock();
+ break;
+ case 'l':
+ printf_nobench("linked list\n");
+ test_percpu_list();
+ break;
+ case 'i':
+ printf_nobench("counter increment\n");
+ test_percpu_inc();
+ break;
+ }
+end:
+ return 0;
+
+error:
+ if (rseq_destroy_lock(&rseq_lock))
+ perror("rseq_destroy_lock");
+ return -1;
+}
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
new file mode 100644
index 0000000..f411be2
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -0,0 +1,200 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <syscall.h>
+#include <assert.h>
+#include <signal.h>
+#include <linux/membarrier.h>
+
+#include "rseq.h"
+
+#ifdef __NR_membarrier
+# define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__)
+#else
+# define membarrier(...) -ENOSYS
+#endif
+
+__thread volatile struct rseq_thread_state __rseq_thread_state = {
+ .abi.u.e.cpu_id = -1,
+};
+
+int rseq_has_sys_membarrier;
+
+static int sys_rseq(volatile struct rseq *rseq_abi, int flags)
+{
+ return syscall(__NR_rseq, rseq_abi, flags);
+}
+
+int rseq_init_current_thread(void)
+{
+ int rc;
+
+ rc = sys_rseq(&__rseq_thread_state.abi, 0);
+ if (rc) {
+ fprintf(stderr, "Error: sys_rseq(...) failed(%d): %s\n",
+ errno, strerror(errno));
+ return -1;
+ }
+ assert(rseq_current_cpu() >= 0);
+ return 0;
+}
+
+int rseq_init_lock(struct rseq_lock *rlock)
+{
+ int ret;
+
+ ret = pthread_mutex_init(&rlock->lock, NULL);
+ if (ret) {
+ errno = ret;
+ return -1;
+ }
+ rlock->state = RSEQ_LOCK_STATE_RESTART;
+ return 0;
+}
+
+int rseq_destroy_lock(struct rseq_lock *rlock)
+{
+ int ret;
+
+ ret = pthread_mutex_destroy(&rlock->lock);
+ if (ret) {
+ errno = ret;
+ return -1;
+ }
+ return 0;
+}
+
+static void signal_off_save(sigset_t *oldset)
+{
+ sigset_t set;
+ int ret;
+
+ sigfillset(&set);
+ ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
+ if (ret)
+ abort();
+}
+
+static void signal_restore(sigset_t oldset)
+{
+ int ret;
+
+ ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+ if (ret)
+ abort();
+}
+
+static void rseq_fallback_lock(struct rseq_lock *rlock)
+{
+ signal_off_save((sigset_t *)&__rseq_thread_state.sigmask_saved);
+ pthread_mutex_lock(&rlock->lock);
+ __rseq_thread_state.fallback_cnt++;
+ /*
+ * For concurrent threads arriving before we set LOCK:
+ * reading cpu_id after setting the state to LOCK
+ * ensures they restart.
+ */
+ ACCESS_ONCE(rlock->state) = RSEQ_LOCK_STATE_LOCK;
+ /*
+ * For concurrent threads arriving after we set LOCK:
+ * those will grab the lock, so we are protected by
+ * mutual exclusion.
+ */
+}
+
+void rseq_fallback_wait(struct rseq_lock *rlock)
+{
+ signal_off_save((sigset_t *)&__rseq_thread_state.sigmask_saved);
+ pthread_mutex_lock(&rlock->lock);
+ __rseq_thread_state.fallback_wait_cnt++;
+ pthread_mutex_unlock(&rlock->lock);
+ signal_restore(__rseq_thread_state.sigmask_saved);
+}
+
+static void rseq_fallback_unlock(struct rseq_lock *rlock, int cpu_at_start)
+{
+ /*
+ * Concurrent rseq arriving before we set state back to RESTART
+ * grab the lock. Those arriving after we set state back to
+ * RESTART will perform restartable critical sections. The next
+ * owner of the lock will take take of making sure it prevents
+ * concurrent restartable sequences from completing. We may be
+ * writing from another CPU, so update the state with a store
+ * release semantic to ensure restartable sections will see our
+ * side effect (writing to *p) before they enter their
+ * restartable critical section.
+ *
+ * In cases where we observe that we are on the right CPU after the
+ * critical section, program order ensures that following restartable
+ * critical sections will see our stores, so we don't have to use
+ * store-release or membarrier.
+ *
+ * Use sys_membarrier when available to remove the memory barrier
+ * implied by smp_load_acquire().
+ */
+ barrier();
+ if (likely(rseq_current_cpu() == cpu_at_start)) {
+ ACCESS_ONCE(rlock->state) = RSEQ_LOCK_STATE_RESTART;
+ } else {
+ if (!has_fast_acquire_release() && rseq_has_sys_membarrier) {
+ if (membarrier(MEMBARRIER_CMD_SHARED, 0))
+ abort();
+ ACCESS_ONCE(rlock->state) = RSEQ_LOCK_STATE_RESTART;
+ } else {
+ /*
+ * Store with release semantic to ensure
+ * restartable sections will see our side effect
+ * (writing to *p) before they enter their
+ * restartable critical section. Matches
+ * smp_load_acquire() in rseq_start().
+ */
+ smp_store_release(&rlock->state,
+ RSEQ_LOCK_STATE_RESTART);
+ }
+ }
+ pthread_mutex_unlock(&rlock->lock);
+ signal_restore(__rseq_thread_state.sigmask_saved);
+}
+
+int rseq_fallback_current_cpu(void)
+{
+ int cpu;
+
+ cpu = sched_getcpu();
+ if (cpu < 0) {
+ perror("sched_getcpu()");
+ abort();
+ }
+ return cpu;
+}
+
+int rseq_fallback_begin(struct rseq_lock *rlock)
+{
+ rseq_fallback_lock(rlock);
+ return rseq_fallback_current_cpu();
+}
+
+void rseq_fallback_end(struct rseq_lock *rlock, int cpu)
+{
+ rseq_fallback_unlock(rlock, cpu);
+}
+
+/* Handle non-initialized rseq for this thread. */
+void rseq_fallback_noinit(struct rseq_state *rseq_state)
+{
+ rseq_state->lock_state = RSEQ_LOCK_STATE_FAIL;
+ rseq_state->cpu_id = 0;
+}
+
+void __attribute__((constructor)) rseq_init(void)
+{
+ int ret;
+
+ ret = membarrier(MEMBARRIER_CMD_QUERY, 0);
+ if (ret >= 0 && (ret & MEMBARRIER_CMD_SHARED))
+ rseq_has_sys_membarrier = 1;
+}
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
new file mode 100644
index 0000000..791e14c
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -0,0 +1,449 @@
+#ifndef RSEQ_H
+#define RSEQ_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <pthread.h>
+#include <signal.h>
+#include <sched.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sched.h>
+#include <linux/rseq.h>
+
+/*
+ * Empty code injection macros, override when testing.
+ * It is important to consider that the ASM injection macros need to be
+ * fully reentrant (e.g. do not modify the stack).
+ */
+#ifndef RSEQ_INJECT_ASM
+#define RSEQ_INJECT_ASM(n)
+#endif
+
+#ifndef RSEQ_INJECT_C
+#define RSEQ_INJECT_C(n)
+#endif
+
+#ifndef RSEQ_INJECT_INPUT
+#define RSEQ_INJECT_INPUT
+#endif
+
+#ifndef RSEQ_INJECT_CLOBBER
+#define RSEQ_INJECT_CLOBBER
+#endif
+
+#ifndef RSEQ_INJECT_FAILED
+#define RSEQ_INJECT_FAILED
+#endif
+
+#ifndef RSEQ_FALLBACK_CNT
+#define RSEQ_FALLBACK_CNT 3
+#endif
+
+struct rseq_thread_state {
+ struct rseq abi; /* Kernel ABI. */
+ uint32_t fallback_wait_cnt;
+ uint32_t fallback_cnt;
+ sigset_t sigmask_saved;
+};
+
+extern __thread volatile struct rseq_thread_state __rseq_thread_state;
+extern int rseq_has_sys_membarrier;
+
+#define likely(x) __builtin_expect(!!(x), 1)
+#define unlikely(x) __builtin_expect(!!(x), 0)
+#define barrier() __asm__ __volatile__("" : : : "memory")
+
+#define ACCESS_ONCE(x) (*(__volatile__ __typeof__(x) *)&(x))
+#define WRITE_ONCE(x, v) __extension__ ({ ACCESS_ONCE(x) = (v); })
+#define READ_ONCE(x) ACCESS_ONCE(x)
+
+#ifdef __x86_64__
+
+#define smp_mb() __asm__ __volatile__ ("mfence" : : : "memory")
+#define smp_rmb() barrier()
+#define smp_wmb() barrier()
+
+#define smp_load_acquire(p) \
+__extension__ ({ \
+ __typeof(*p) ____p1 = READ_ONCE(*p); \
+ barrier(); \
+ ____p1; \
+})
+
+#define smp_acquire__after_ctrl_dep() smp_rmb()
+
+#define smp_store_release(p, v) \
+do { \
+ barrier(); \
+ WRITE_ONCE(*p, v); \
+} while (0)
+
+#define has_fast_acquire_release() 1
+#define has_single_copy_load_64() 1
+
+#elif __i386__
+
+/*
+ * Support older 32-bit architectures that do not implement fence
+ * instructions.
+ */
+#define smp_mb() \
+ __asm__ __volatile__ ("lock; addl $0,0(%%esp)" : : : "memory")
+#define smp_rmb() \
+ __asm__ __volatile__ ("lock; addl $0,0(%%esp)" : : : "memory")
+#define smp_wmb() \
+ __asm__ __volatile__ ("lock; addl $0,0(%%esp)" : : : "memory")
+
+#define smp_load_acquire(p) \
+__extension__ ({ \
+ __typeof(*p) ____p1 = READ_ONCE(*p); \
+ smp_mb(); \
+ ____p1; \
+})
+
+#define smp_acquire__after_ctrl_dep() smp_rmb()
+
+#define smp_store_release(p, v) \
+do { \
+ smp_mb(); \
+ WRITE_ONCE(*p, v); \
+} while (0)
+
+#define has_fast_acquire_release() 0
+#define has_single_copy_load_64() 0
+
+#elif defined(__ARMEL__)
+
+#define smp_mb() __asm__ __volatile__ ("dmb" : : : "memory")
+#define smp_rmb() __asm__ __volatile__ ("dmb" : : : "memory")
+#define smp_wmb() __asm__ __volatile__ ("dmb" : : : "memory")
+
+#define smp_load_acquire(p) \
+__extension__ ({ \
+ __typeof(*p) ____p1 = READ_ONCE(*p); \
+ smp_mb(); \
+ ____p1; \
+})
+
+#define smp_acquire__after_ctrl_dep() smp_rmb()
+
+#define smp_store_release(p, v) \
+do { \
+ smp_mb(); \
+ WRITE_ONCE(*p, v); \
+} while (0)
+
+#define has_fast_acquire_release() 0
+#define has_single_copy_load_64() 1
+
+#else
+#error unsupported target
+#endif
+
+enum rseq_lock_state {
+ RSEQ_LOCK_STATE_RESTART = 0,
+ RSEQ_LOCK_STATE_LOCK = 1,
+ RSEQ_LOCK_STATE_FAIL = 2,
+};
+
+struct rseq_lock {
+ pthread_mutex_t lock;
+ int32_t state; /* enum rseq_lock_state */
+};
+
+/* State returned by rseq_start, passed as argument to rseq_finish. */
+struct rseq_state {
+ volatile struct rseq_thread_state *rseqp;
+ int32_t cpu_id; /* cpu_id at start. */
+ uint32_t event_counter; /* event_counter at start. */
+ int32_t lock_state; /* Lock state at start. */
+};
+
+/*
+ * Initialize rseq for the current thread. Must be called once by any
+ * thread which uses restartable sequences, before they start using
+ * restartable sequences. If initialization is not invoked, or if it
+ * fails, the restartable critical sections will fall-back on locking
+ * (rseq_lock).
+ */
+int rseq_init_current_thread(void);
+
+/*
+ * The fallback lock should be initialized before being used by any
+ * thread, and destroyed after all threads are done using it. This lock
+ * should be used by all rseq calls associated with shared data, either
+ * between threads, or between processes in a shared memory.
+ *
+ * There may be many rseq_lock per process, e.g. one per protected data
+ * structure.
+ */
+int rseq_init_lock(struct rseq_lock *rlock);
+int rseq_destroy_lock(struct rseq_lock *rlock);
+
+/*
+ * Restartable sequence fallback prototypes. Fallback on locking when
+ * rseq is not initialized, not available on the system, or during
+ * single-stepping to ensure forward progress.
+ */
+int rseq_fallback_begin(struct rseq_lock *rlock);
+void rseq_fallback_end(struct rseq_lock *rlock, int cpu);
+void rseq_fallback_wait(struct rseq_lock *rlock);
+void rseq_fallback_noinit(struct rseq_state *rseq_state);
+
+/*
+ * Restartable sequence fallback for reading the current CPU number.
+ */
+int rseq_fallback_current_cpu(void);
+
+static inline int32_t rseq_cpu_at_start(struct rseq_state start_value)
+{
+ return start_value.cpu_id;
+}
+
+static inline int32_t rseq_current_cpu_raw(void)
+{
+ return ACCESS_ONCE(__rseq_thread_state.abi.u.e.cpu_id);
+}
+
+static inline int32_t rseq_current_cpu(void)
+{
+ int32_t cpu;
+
+ cpu = rseq_current_cpu_raw();
+ if (unlikely(cpu < 0))
+ cpu = rseq_fallback_current_cpu();
+ return cpu;
+}
+
+static inline __attribute__((always_inline))
+struct rseq_state rseq_start(struct rseq_lock *rlock)
+{
+ struct rseq_state result;
+
+ result.rseqp = &__rseq_thread_state;
+ if (has_single_copy_load_64()) {
+ union {
+ struct {
+ uint32_t cpu_id;
+ uint32_t event_counter;
+ } e;
+ uint64_t v;
+ } u;
+
+ u.v = ACCESS_ONCE(result.rseqp->abi.u.v);
+ result.event_counter = u.e.event_counter;
+ result.cpu_id = u.e.cpu_id;
+ } else {
+ result.event_counter =
+ ACCESS_ONCE(result.rseqp->abi.u.e.event_counter);
+ /* load event_counter before cpu_id. */
+ RSEQ_INJECT_C(5)
+ result.cpu_id = ACCESS_ONCE(result.rseqp->abi.u.e.cpu_id);
+ }
+ /*
+ * Read event counter before lock state and cpu_id. This ensures
+ * that when the state changes from RESTART to LOCK, if we have
+ * some threads that have already seen the RESTART still in
+ * flight, they will necessarily be preempted/signalled before a
+ * thread can see the LOCK state for that same CPU. That
+ * preemption/signalling will cause them to restart, so they
+ * don't interfere with the lock.
+ */
+ RSEQ_INJECT_C(6)
+
+ if (!has_fast_acquire_release() && likely(rseq_has_sys_membarrier)) {
+ result.lock_state = ACCESS_ONCE(rlock->state);
+ barrier();
+ } else {
+ /*
+ * Load lock state with acquire semantic. Matches
+ * smp_store_release() in rseq_fallback_end().
+ */
+ result.lock_state = smp_load_acquire(&rlock->state);
+ }
+ if (unlikely(result.cpu_id < 0))
+ rseq_fallback_noinit(&result);
+ /*
+ * We need to ensure that the compiler does not re-order the
+ * loads of any protected values before we read the current
+ * state.
+ */
+ barrier();
+ return result;
+}
+
+static inline __attribute__((always_inline))
+bool rseq_finish(struct rseq_lock *rlock,
+ intptr_t *p, intptr_t to_write,
+ struct rseq_state start_value)
+{
+ RSEQ_INJECT_C(9)
+
+ if (unlikely(start_value.lock_state != RSEQ_LOCK_STATE_RESTART)) {
+ if (start_value.lock_state == RSEQ_LOCK_STATE_LOCK)
+ rseq_fallback_wait(rlock);
+ return false;
+ }
+
+#ifdef __x86_64__
+ /*
+ * The __rseq_table section can be used by debuggers to better
+ * handle single-stepping through the restartable critical
+ * sections.
+ */
+ __asm__ __volatile__ goto (
+ ".pushsection __rseq_table, \"aw\"\n\t"
+ ".balign 8\n\t"
+ "4:\n\t"
+ ".quad 1f, 2f, 3f\n\t"
+ ".popsection\n\t"
+ "1:\n\t"
+ RSEQ_INJECT_ASM(1)
+ "movq $4b, (%[rseq_cs])\n\t"
+ RSEQ_INJECT_ASM(2)
+ "cmpl %[start_event_counter], %[current_event_counter]\n\t"
+ "jnz 3f\n\t"
+ RSEQ_INJECT_ASM(3)
+ "movq %[to_write], (%[target])\n\t"
+ "2:\n\t"
+ RSEQ_INJECT_ASM(4)
+ "movq $0, (%[rseq_cs])\n\t"
+ "jmp %l[succeed]\n\t"
+ "3: movq $0, (%[rseq_cs])\n\t"
+ : /* no outputs */
+ : [start_event_counter]"r"(start_value.event_counter),
+ [current_event_counter]"m"(start_value.rseqp->abi.u.e.event_counter),
+ [to_write]"r"(to_write),
+ [target]"r"(p),
+ [rseq_cs]"r"(&start_value.rseqp->abi.rseq_cs)
+ RSEQ_INJECT_INPUT
+ : "memory", "cc"
+ RSEQ_INJECT_CLOBBER
+ : succeed
+ );
+#elif defined(__i386__)
+ /*
+ * The __rseq_table section can be used by debuggers to better
+ * handle single-stepping through the restartable critical
+ * sections.
+ */
+ __asm__ __volatile__ goto (
+ ".pushsection __rseq_table, \"aw\"\n\t"
+ ".balign 8\n\t"
+ "4:\n\t"
+ ".long 1f, 0x0, 2f, 0x0, 3f, 0x0\n\t"
+ ".popsection\n\t"
+ "1:\n\t"
+ RSEQ_INJECT_ASM(1)
+ "movl $4b, (%[rseq_cs])\n\t"
+ RSEQ_INJECT_ASM(2)
+ "cmpl %[start_event_counter], %[current_event_counter]\n\t"
+ "jnz 3f\n\t"
+ RSEQ_INJECT_ASM(3)
+ "movl %[to_write], (%[target])\n\t"
+ "2:\n\t"
+ RSEQ_INJECT_ASM(4)
+ "movl $0, (%[rseq_cs])\n\t"
+ "jmp %l[succeed]\n\t"
+ "3: movl $0, (%[rseq_cs])\n\t"
+ : /* no outputs */
+ : [start_event_counter]"r"(start_value.event_counter),
+ [current_event_counter]"m"(start_value.rseqp->abi.u.e.event_counter),
+ [to_write]"r"(to_write),
+ [target]"r"(p),
+ [rseq_cs]"r"(&start_value.rseqp->abi.rseq_cs)
+ RSEQ_INJECT_INPUT
+ : "memory", "cc"
+ RSEQ_INJECT_CLOBBER
+ : succeed
+ );
+#elif defined(__ARMEL__)
+ {
+ /*
+ * The __rseq_table section can be used by debuggers to better
+ * handle single-stepping through the restartable critical
+ * sections.
+ */
+ __asm__ __volatile__ goto (
+ ".pushsection __rseq_table, \"aw\"\n\t"
+ ".balign 8\n\t"
+ ".word 1f, 0x0, 2f, 0x0, 3f, 0x0\n\t"
+ ".popsection\n\t"
+ "1:\n\t"
+ RSEQ_INJECT_ASM(1)
+ "adr r0, 4f\n\t"
+ "str r0, [%[rseq_cs]]\n\t"
+ RSEQ_INJECT_ASM(2)
+ "ldr r0, %[current_event_counter]\n\t"
+ "mov r1, #0\n\t"
+ "cmp %[start_event_counter], r0\n\t"
+ "bne 3f\n\t"
+ RSEQ_INJECT_ASM(3)
+ "str %[to_write], [%[target]]\n\t"
+ "2:\n\t"
+ RSEQ_INJECT_ASM(4)
+ "str r1, [%[rseq_cs]]\n\t"
+ "b %l[succeed]\n\t"
+ ".balign 8\n\t"
+ "4:\n\t"
+ ".word 1b, 0x0, 2b, 0x0, 3f, 0x0\n\t"
+ "3:\n\t"
+ "mov r1, #0\n\t"
+ "str r1, [%[rseq_cs]]\n\t"
+ : /* no outputs */
+ : [start_event_counter]"r"(start_value.event_counter),
+ [current_event_counter]"m"(start_value.rseqp->abi.u.e.event_counter),
+ [to_write]"r"(to_write),
+ [rseq_cs]"r"(&start_value.rseqp->abi.rseq_cs),
+ [target]"r"(p)
+ RSEQ_INJECT_INPUT
+ : "r0", "r1", "memory", "cc"
+ RSEQ_INJECT_CLOBBER
+ : succeed
+ );
+ }
+#else
+#error unsupported target
+#endif
+ RSEQ_INJECT_FAILED
+ return false;
+succeed:
+ return true;
+}
+
+/*
+ * Helper macro doing two restartable critical section attempts, and if
+ * they fail, fallback on locking.
+ */
+#define do_rseq(_lock, _rseq_state, _cpu, _result, _targetptr, _newval, \
+ _code) \
+ do { \
+ _rseq_state = rseq_start(_lock); \
+ _cpu = rseq_cpu_at_start(_rseq_state); \
+ _result = true; \
+ _code \
+ if (unlikely(!_result)) \
+ break; \
+ if (likely(rseq_finish(_lock, _targetptr, _newval, \
+ _rseq_state))) \
+ break; \
+ _rseq_state = rseq_start(_lock); \
+ _cpu = rseq_cpu_at_start(_rseq_state); \
+ _result = true; \
+ _code \
+ if (unlikely(!_result)) \
+ break; \
+ if (likely(rseq_finish(_lock, _targetptr, _newval, \
+ _rseq_state))) \
+ break; \
+ _cpu = rseq_fallback_begin(_lock); \
+ _result = true; \
+ _code \
+ if (likely(_result)) \
+ *(_targetptr) = (_newval); \
+ rseq_fallback_end(_lock, _cpu); \
+ } while (0)
+
+#endif /* RSEQ_H_ */
--
2.1.4
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