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KAGA-KOKOPeter Zijlstra
KAGA-KOKO
authored and
Peter Zijlstra
committed
selftests/rseq: Implement time slice extension test
Provide an initial test case to evaluate the functionality. This needs to be extended to cover the ABI violations and expose the race condition between observing granted and arriving in rseq_slice_yield(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20251215155709.320325431@linutronix.de
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‎tools/testing/selftests/rseq/.gitignore‎

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@@ -10,3 +10,4 @@ param_test_mm_cid
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param_test_mm_cid_benchmark
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param_test_mm_cid_compare_twice
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syscall_errors_test
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slice_test

‎tools/testing/selftests/rseq/Makefile‎

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@@ -17,7 +17,7 @@ OVERRIDE_TARGETS = 1
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TEST_GEN_PROGS = basic_test basic_percpu_ops_test basic_percpu_ops_mm_cid_test param_test \
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param_test_benchmark param_test_compare_twice param_test_mm_cid \
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param_test_mm_cid_benchmark param_test_mm_cid_compare_twice \
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syscall_errors_test
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syscall_errors_test slice_test
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TEST_GEN_PROGS_EXTENDED = librseq.so
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@@ -59,3 +59,6 @@ $(OUTPUT)/param_test_mm_cid_compare_twice: param_test.c $(TEST_GEN_PROGS_EXTENDE
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$(OUTPUT)/syscall_errors_test: syscall_errors_test.c $(TEST_GEN_PROGS_EXTENDED) \
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rseq.h rseq-*.h
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$(CC) $(CFLAGS) $< $(LDLIBS) -lrseq -o $@
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$(OUTPUT)/slice_test: slice_test.c $(TEST_GEN_PROGS_EXTENDED) rseq.h rseq-*.h
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$(CC) $(CFLAGS) $< $(LDLIBS) -lrseq -o $@

‎tools/testing/selftests/rseq/rseq-abi.h‎

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@@ -53,6 +53,27 @@ struct rseq_abi_cs {
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__u64 abort_ip;
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} __attribute__((aligned(4 * sizeof(__u64))));
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/**
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* rseq_abi_slice_ctrl - Time slice extension control structure
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* @all: Compound value
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* @request: Request for a time slice extension
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* @granted: Granted time slice extension
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*
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* @request is set by user space and can be cleared by user space or kernel
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* space. @granted is set and cleared by the kernel and must only be read
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* by user space.
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*/
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struct rseq_abi_slice_ctrl {
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union {
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__u32 all;
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struct {
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__u8 request;
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__u8 granted;
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__u16 __reserved;
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};
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};
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};
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/*
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* struct rseq_abi is aligned on 4 * 8 bytes to ensure it is always
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* contained within a single cache-line.
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*/
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__u32 mm_cid;
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/*
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* Time slice extension control structure. CPU local updates from
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* kernel and user space.
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*/
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struct rseq_abi_slice_ctrl slice_ctrl;
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/*
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* Flexible array member at end of structure, after last feature field.
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*/

‎tools/testing/selftests/rseq/slice_test.c‎

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// SPDX-License-Identifier: LGPL-2.1
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#define _GNU_SOURCE
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#include <assert.h>
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#include <pthread.h>
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#include <sched.h>
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#include <signal.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <string.h>
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#include <syscall.h>
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#include <unistd.h>
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#include <linux/prctl.h>
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#include <sys/prctl.h>
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#include <sys/time.h>
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#include "rseq.h"
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#include "../kselftest_harness.h"
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#ifndef __NR_rseq_slice_yield
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# define __NR_rseq_slice_yield 471
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#endif
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#define BITS_PER_INT 32
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#define BITS_PER_BYTE 8
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#ifndef PR_RSEQ_SLICE_EXTENSION
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# define PR_RSEQ_SLICE_EXTENSION 79
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# define PR_RSEQ_SLICE_EXTENSION_GET 1
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# define PR_RSEQ_SLICE_EXTENSION_SET 2
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# define PR_RSEQ_SLICE_EXT_ENABLE 0x01
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#endif
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#ifndef RSEQ_SLICE_EXT_REQUEST_BIT
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# define RSEQ_SLICE_EXT_REQUEST_BIT 0
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# define RSEQ_SLICE_EXT_GRANTED_BIT 1
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#endif
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#ifndef asm_inline
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# define asm_inline asm __inline
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#endif
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#define NSEC_PER_SEC 1000000000L
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#define NSEC_PER_USEC 1000L
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struct noise_params {
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int64_t noise_nsecs;
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int64_t sleep_nsecs;
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int64_t run;
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};
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FIXTURE(slice_ext)
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{
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pthread_t noise_thread;
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struct noise_params noise_params;
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};
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FIXTURE_VARIANT(slice_ext)
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{
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int64_t total_nsecs;
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int64_t slice_nsecs;
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int64_t noise_nsecs;
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int64_t sleep_nsecs;
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bool no_yield;
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};
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FIXTURE_VARIANT_ADD(slice_ext, n2_2_50)
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{
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.total_nsecs = 5LL * NSEC_PER_SEC,
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.slice_nsecs = 2LL * NSEC_PER_USEC,
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.noise_nsecs = 2LL * NSEC_PER_USEC,
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.sleep_nsecs = 50LL * NSEC_PER_USEC,
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};
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FIXTURE_VARIANT_ADD(slice_ext, n50_2_50)
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{
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.total_nsecs = 5LL * NSEC_PER_SEC,
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.slice_nsecs = 50LL * NSEC_PER_USEC,
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.noise_nsecs = 2LL * NSEC_PER_USEC,
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.sleep_nsecs = 50LL * NSEC_PER_USEC,
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};
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FIXTURE_VARIANT_ADD(slice_ext, n2_2_50_no_yield)
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{
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.total_nsecs = 5LL * NSEC_PER_SEC,
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.slice_nsecs = 2LL * NSEC_PER_USEC,
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.noise_nsecs = 2LL * NSEC_PER_USEC,
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.sleep_nsecs = 50LL * NSEC_PER_USEC,
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.no_yield = true,
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};
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static inline bool elapsed(struct timespec *start, struct timespec *now,
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int64_t span)
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{
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int64_t delta = now->tv_sec - start->tv_sec;
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delta *= NSEC_PER_SEC;
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delta += now->tv_nsec - start->tv_nsec;
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return delta >= span;
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}
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static void *noise_thread(void *arg)
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{
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struct noise_params *p = arg;
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while (RSEQ_READ_ONCE(p->run)) {
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struct timespec ts_start, ts_now;
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clock_gettime(CLOCK_MONOTONIC, &ts_start);
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do {
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clock_gettime(CLOCK_MONOTONIC, &ts_now);
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} while (!elapsed(&ts_start, &ts_now, p->noise_nsecs));
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ts_start.tv_sec = 0;
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ts_start.tv_nsec = p->sleep_nsecs;
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clock_nanosleep(CLOCK_MONOTONIC, 0, &ts_start, NULL);
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}
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return NULL;
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}
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FIXTURE_SETUP(slice_ext)
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{
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cpu_set_t affinity;
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ASSERT_EQ(sched_getaffinity(0, sizeof(affinity), &affinity), 0);
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/* Pin it on a single CPU. Avoid CPU 0 */
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for (int i = 1; i < CPU_SETSIZE; i++) {
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if (!CPU_ISSET(i, &affinity))
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continue;
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CPU_ZERO(&affinity);
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CPU_SET(i, &affinity);
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ASSERT_EQ(sched_setaffinity(0, sizeof(affinity), &affinity), 0);
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break;
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}
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ASSERT_EQ(rseq_register_current_thread(), 0);
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ASSERT_EQ(prctl(PR_RSEQ_SLICE_EXTENSION, PR_RSEQ_SLICE_EXTENSION_SET,
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PR_RSEQ_SLICE_EXT_ENABLE, 0, 0), 0);
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self->noise_params.noise_nsecs = variant->noise_nsecs;
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self->noise_params.sleep_nsecs = variant->sleep_nsecs;
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self->noise_params.run = 1;
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ASSERT_EQ(pthread_create(&self->noise_thread, NULL, noise_thread, &self->noise_params), 0);
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}
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FIXTURE_TEARDOWN(slice_ext)
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{
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self->noise_params.run = 0;
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pthread_join(self->noise_thread, NULL);
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}
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TEST_F(slice_ext, slice_test)
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{
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unsigned long success = 0, yielded = 0, scheduled = 0, raced = 0;
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unsigned long total = 0, aborted = 0;
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struct rseq_abi *rs = rseq_get_abi();
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struct timespec ts_start, ts_now;
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ASSERT_NE(rs, NULL);
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clock_gettime(CLOCK_MONOTONIC, &ts_start);
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do {
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struct timespec ts_cs;
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bool req = false;
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clock_gettime(CLOCK_MONOTONIC, &ts_cs);
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total++;
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RSEQ_WRITE_ONCE(rs->slice_ctrl.request, 1);
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do {
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clock_gettime(CLOCK_MONOTONIC, &ts_now);
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} while (!elapsed(&ts_cs, &ts_now, variant->slice_nsecs));
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/*
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* request can be cleared unconditionally, but for making
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* the stats work this is actually checking it first
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*/
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if (RSEQ_READ_ONCE(rs->slice_ctrl.request)) {
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RSEQ_WRITE_ONCE(rs->slice_ctrl.request, 0);
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/* Race between check and clear! */
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req = true;
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success++;
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}
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if (RSEQ_READ_ONCE(rs->slice_ctrl.granted)) {
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/* The above raced against a late grant */
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if (req)
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success--;
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if (variant->no_yield) {
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syscall(__NR_getpid);
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aborted++;
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} else {
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yielded++;
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if (!syscall(__NR_rseq_slice_yield))
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raced++;
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}
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} else {
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if (!req)
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scheduled++;
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}
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clock_gettime(CLOCK_MONOTONIC, &ts_now);
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} while (!elapsed(&ts_start, &ts_now, variant->total_nsecs));
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printf("# Total %12ld\n", total);
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printf("# Success %12ld\n", success);
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printf("# Yielded %12ld\n", yielded);
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printf("# Aborted %12ld\n", aborted);
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printf("# Scheduled %12ld\n", scheduled);
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printf("# Raced %12ld\n", raced);
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}
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TEST_HARNESS_MAIN

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