blktrace exit directly when nthreads running patch

blktrace-fix-exit-directly-when-nthreads-running.patch

@@ -0,0 +1,65 @@
+From 3a1b1366d30375cdb0f5b299df4edda0c8ba3bcc Mon Sep 17 00:00:00 2001
+From: lijinlin <lijinlin3@huawei.com>
+Date: Mon, 28 Jun 2021 13:41:32 -0600
+Subject: 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 <lijinlin3@huawei.com>
+Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
+Signed-off-by: Lixiaokeng <lixiaokeng@huawei.com>
+Signed-off-by: Jens Axboe <axboe@kernel.dk>
+---
+ blktrace.c | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+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)
+ 			alarm(stop_watch);
+-	} else
++	} else {
+ 		stop_tracers();
++		done = 1;
++	}
+ 
+ 	wait_tracers();
+ 	if (nthreads_running == ncpus)
+-- 
+cgit 1.2.3-1.el7
+

blktrace.spec

@@ -1,6 +1,6 @@
 Name:    blktrace
 Version: 1.2.0
-Release: 17
+Release: 18
 Summary: Block IO tracer in the Linux kernel
 License: GPLv2+
 Source:  http://brick.kernel.dk/snaps/blktrace-%{version}.tar.bz2
@@ -14,6 +14,7 @@ Requires:      python3
 Patch0: blktrace-fix-btt-overflow.patch
 Patch1: remove-python2-dependency.patch
 Patch2: modify-python2-expression-to-python3.patch
+Patch3: blktrace-fix-exit-directly-when-nthreads-running.patch 
 
 %description
 blktrace is a block layer IO tracing mechanism which provides detailed
@@ -48,6 +49,9 @@ make dest=%{buildroot} prefix=%{buildroot}/%{_prefix} mandir=%{buildroot}/%{_man
 %{_mandir}/man8/*
 
 %changelog
+* Mon Jul 05 2021 linxiaoran<linxiaoran@huawei.com> - 1.2.0-18
+- blktrace fix exit direclty when nthreads running
+
 * Tue Feb 9 2021 Zhiqiang Liu<liuzhiqiang26@huawei.com> - 1.2.0-17
 - set release num to 17 for CI