The nr_cpus = CPU_COUNT(&possible_mask) is the number of available CPUs in possible_mask. As a result, the "cpu = i % nr_cpus" may always return CPU that is not available in possible_mask.
Suppose the server has 8 CPUs. The below Failure is encountered immediately if the task is bound to CPU 5 and 6.
==== Test Assertion Failure ==== rseq_test.c:228: i > (NR_TASK_MIGRATIONS / 2) pid=10127 tid=10127 errno=4 - Interrupted system call 1 0x00000000004018e5: main at rseq_test.c:227 2 0x00007fcc8fc66bf6: ?? ??:0 3 0x0000000000401959: _start at ??:? Only performed 4 KVM_RUNs, task stalled too much?
Signed-off-by: Dongli Zhang dongli.zhang@oracle.com --- tools/testing/selftests/kvm/rseq_test.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c index c5e0dd664a7b..41df5173970c 100644 --- a/tools/testing/selftests/kvm/rseq_test.c +++ b/tools/testing/selftests/kvm/rseq_test.c @@ -10,6 +10,7 @@ #include <signal.h> #include <syscall.h> #include <sys/ioctl.h> +#include <sys/sysinfo.h> #include <asm/barrier.h> #include <linux/atomic.h> #include <linux/rseq.h> @@ -43,6 +44,18 @@ static bool done;
static atomic_t seq_cnt;
+static int get_max_cpu_idx(void) +{ + int nproc = get_nprocs_conf(); + int i, max = -ENOENT; + + for (i = 0; i < nproc; i++) + if (CPU_ISSET(i, &possible_mask)) + max = i; + + return max; +} + static void guest_code(void) { for (;;) @@ -61,10 +74,13 @@ static void *migration_worker(void *ign) { cpu_set_t allowed_mask; int r, i, nr_cpus, cpu; + int max_cpu_idx;
CPU_ZERO(&allowed_mask);
- nr_cpus = CPU_COUNT(&possible_mask); + max_cpu_idx = get_max_cpu_idx(); + TEST_ASSERT(max_cpu_idx >= 0, "Invalid possible_mask"); + nr_cpus = max_cpu_idx + 1;
for (i = 0; i < NR_TASK_MIGRATIONS; i++) { cpu = i % nr_cpus;