[PATCH] perf test: Skip perf bench breakpoint run if no breakpoints available

[Kajol Jain]

Based on commit 7d54a4acd8c1 ("perf test: Skip watchpoint
tests if no watchpoints available"), hardware breakpoints
are not available for power9 platform and because of that
perf bench breakpoint run fails on power9 platform.
Add code to check for the return value of perf_event_open()
in breakpoint run and skip the perf bench breakpoint run,
if hardware breakpoints are not available.

Result on power9 system before patch changes:
[command]# perf bench breakpoint thread
perf_event_open: No such device

Result on power9 system after patch changes:
[command]# ./perf bench breakpoint thread
Skipping perf bench breakpoint thread: No hardware support

Reported-by: Disha Goel <disg...@linux.vnet.ibm.com>
Signed-off-by: Kajol Jain <kj...@linux.ibm.com>
---
 tools/perf/bench/breakpoint.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/tools/perf/bench/breakpoint.c b/tools/perf/bench/breakpoint.c
index 41385f89ffc7..dfd18f5db97d 100644
--- a/tools/perf/bench/breakpoint.c
+++ b/tools/perf/bench/breakpoint.c
@@ -47,6 +47,7 @@ struct breakpoint {
 static int breakpoint_setup(void *addr)
 {
        struct perf_event_attr attr = { .size = 0, };
+       int fd;
 
        attr.type = PERF_TYPE_BREAKPOINT;
        attr.size = sizeof(attr);
@@ -56,7 +57,12 @@ static int breakpoint_setup(void *addr)
        attr.bp_addr = (unsigned long)addr;
        attr.bp_type = HW_BREAKPOINT_RW;
        attr.bp_len = HW_BREAKPOINT_LEN_1;
-       return syscall(SYS_perf_event_open, &attr, 0, -1, -1, 0);
+       fd = syscall(SYS_perf_event_open, &attr, 0, -1, -1, 0);
+
+       if (fd < 0)
+               fd = -errno;
+
+       return fd;
 }
 
 static void *passive_thread(void *arg)
@@ -122,8 +128,14 @@ int bench_breakpoint_thread(int argc, const char **argv)
 
        for (i = 0; i < thread_params.nbreakpoints; i++) {
                breakpoints[i].fd = breakpoint_setup(&breakpoints[i].watched);
-               if (breakpoints[i].fd == -1)
+
+               if (breakpoints[i].fd < 0) {
+                       if (breakpoints[i].fd == -ENODEV) {
+                               printf("Skipping perf bench breakpoint thread: 
No hardware support\n");
+                               return 0;
+                       }
                        exit((perror("perf_event_open"), EXIT_FAILURE));
+               }
        }
        gettimeofday(&start, NULL);
        for (i = 0; i < thread_params.nparallel; i++) {
@@ -196,8 +208,14 @@ int bench_breakpoint_enable(int argc, const char **argv)
                exit(EXIT_FAILURE);
        }
        fd = breakpoint_setup(&watched);
-       if (fd == -1)
+
+       if (fd < 0) {
+               if (fd == -ENODEV) {
+                       printf("Skipping perf bench breakpoint enable: No 
hardware support\n");
+                       return 0;
+               }
                exit((perror("perf_event_open"), EXIT_FAILURE));
+       }
        nthreads = enable_params.npassive + enable_params.nactive;
        threads = calloc(nthreads, sizeof(threads[0]));
        if (!threads)
-- 
2.39.3