!26 blktrace bug fix

From: @lin-xiaoran
Reviewed-by: @liuzhiqiang26
Signed-off-by: @liuzhiqiang26

0016-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: 16
+Release: 17
 Summary: Block IO tracer in the Linux kernel
 License: GPLv2+
 Source:  http://brick.kernel.dk/snaps/blktrace-%{version}.tar.bz2
@@ -24,6 +24,7 @@ Patch12: 0012-btt_plot.py-Use-with-open-as-.-context-manager.patch
 Patch13: 0013-blkparse-Fix-device-in-event-tracking-error-messages.patch
 Patch14: 0014-blkparse-Allow-request-tracking-on-non-md-dm-devices.patch
 Patch15: 0015-blkparse-Initialize-and-test-for-undefined-request-t.patch
+Patch16: 0016-blktrace-fix-exit-directly-when-nthreads-running.patch
 
 %description
 blktrace is a block layer IO tracing mechanism which provides detailed
@@ -88,6 +89,9 @@ comparing the differences between different benchmark runs.
 %{_mandir}/man1/iowatcher.*
 
 %changelog
+* Fri Jul 02 2021 linxiaoran <linxiaoran@huawei.com> - 1.2.0-17
+- Fix blktrace exit patch
+
 * Thu Sep 10 2020 lihaotian <lihaotian9@huawei.com> - 1.2.0-16
 - create iowatcher rpm sub-package