path: root/blktrace.c
diff options
authorlijinlin <>2021-06-28 13:41:32 -0600
committerJens Axboe <>2021-06-28 13:41:32 -0600
commit3a1b1366d30375cdb0f5b299df4edda0c8ba3bcc (patch)
tree3fa30366187790a1a9465d8150f1febcbd9d291b /blktrace.c
parent366d30b9cdb20345c5d064af850d686da79b89eb (diff)
blktrace: exit directly when nthreads_running != ncpus in run_tracers()
We found blktrace got stuck when cgroup restricts blktrace to use cpu, the messages and stack is: [root@localhost ~]# blktrace -w 10 -o- /dev/sda FAILED to start thread on CPU 1: 22/Invalid argument FAILED to start thread on CPU 2: 22/Invalid argument [root@localhost ~]# cat /proc/1385110/stack [<0>] __switch_to+0xe8/0x150 [<0>] futex_wait_queue_me+0xd4/0x158 [<0>] futex_wait+0xf4/0x230 [<0>] do_futex+0x470/0x900 [<0>] __arm64_sys_futex+0x13c/0x188 [<0>] el0_svc_common+0x80/0x200 [<0>] el0_svc_handler+0x78/0xe0 [<0>] el0_svc+0x10/0x260 [<0>] 0xffffffffffffffff Blktrace failed to start thread is caused by thread can't lock on the Restricted cpu. In this case, blktrace would't schedule an alarm after defined time to set variable 'done' as 1. We debug the code and found the call trace as bellow: main() ==>run_tracers() ==>wait_tracers() ==>process_trace_bufs() ==>wait_empty_entries() ==>t_pthread_cond_wait() Blktrace was set to piped output, so the process is stuck in wait_empty_entries() for wait variable 'done' have been set as 1. We set variable 'done' as 1 when 'nthreads_running' is not equal to 'ncpus' in run_tracers() to fix the problem. Signed-off-by: lijinlin <> Signed-off-by: Zhiqiang Liu <> Signed-off-by: Lixiaokeng <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'blktrace.c')
1 files changed, 3 insertions, 1 deletions
diff --git a/blktrace.c b/blktrace.c
index 82a6aad..3444fbb 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -2705,8 +2705,10 @@ static int run_tracers(void)
printf("blktrace: connected!\n");
if (stop_watch)
- } else
+ } else {
+ done = 1;
+ }
if (nthreads_running == ncpus)