Re: [Qemu-block] [PATCH 1/1] qemu-iotests/109: Fix lock race condition

[Jeff Cody]

On Tue, Aug 01, 2017 at 05:31:27PM -0400, Cleber Rosa wrote:
> A race condition is currently present between the clean up attempt of
> the QEMU process and the execution of qemu-img.  The actual (bad)
> output is:
> 
>  -Warning: Image size mismatch!
>  -Images are identical.
>  +qemu-img: Could not open '/tests/qemu-iotests/scratch/t.raw': 
> Failed to get "consistent read" lock
>  +Is another process using the image?
> 
> A KILL signal is sent to the QEMU process, but qemu-img may begin to
> run before the QEMU process is really gone.  qemu-img will then
> attempt to open the TEST_IMG file before it can secure a lock on it.
> 
> This attempts a more graceful shutdown, and waits for the QEMU process
> to exit.
> 
> Signed-off-by: Cleber Rosa 


Reviewed-by: Jeff Cody 


> ---
>  tests/qemu-iotests/109 |  3 ++-
>  tests/qemu-iotests/109.out | 56 
> ++
>  2 files changed, 58 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/qemu-iotests/109 b/tests/qemu-iotests/109
> index 3b496a3..d70b574 100755
> --- a/tests/qemu-iotests/109
> +++ b/tests/qemu-iotests/109
> @@ -67,7 +67,8 @@ function run_qemu()
>  _send_qemu_cmd $QEMU_HANDLE '' "BLOCK_JOB_COMPLETED"
>  fi
>  _send_qemu_cmd $QEMU_HANDLE '{"execute":"query-block-jobs"}' "return"
> -_cleanup_qemu
> +_send_qemu_cmd $QEMU_HANDLE '{"execute":"quit"}' "return"
> +wait=1 _cleanup_qemu
>  }
>  
>  for fmt in qcow qcow2 qed vdi vmdk vpc; do
> diff --git a/tests/qemu-iotests/109.out b/tests/qemu-iotests/109.out
> index dc02f9e..c189e28 100644
> --- a/tests/qemu-iotests/109.out
> +++ b/tests/qemu-iotests/109.out
> @@ -12,12 +12,17 @@ Specify the 'raw' format explicitly to remove the 
> restrictions.
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": 
> "report"}}
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": LEN, "offset": 0, 
> "speed": 0, "type": "mirror", "error": "Operation not permitted"}}
>  {"return": []}
> +{"return": {}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "SHUTDOWN", "data": {"guest": false}}
>  read 65536/65536 bytes at offset 0
>  64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>  {"return": {}}
>  {"return": {}}
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_READY", "data": {"device": "src", "len": 1024, "offset": 1024, 
> "speed": 0, "type": "mirror"}}
>  {"return": [{"io-status": "ok", "device": "src", "busy": false, "len": 1024, 
> "offset": 1024, "paused": false, "speed": 0, "ready": true, "type": 
> "mirror"}]}
> +{"return": {}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "SHUTDOWN", "data": {"guest": false}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 1024, "offset": 1024, 
> "speed": 0, "type": "mirror"}}
>  Warning: Image size mismatch!
>  Images are identical.
>  
> @@ -33,12 +38,17 @@ Specify the 'raw' format explicitly to remove the 
> restrictions.
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": 
> "report"}}
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": LEN, "offset": 512, 
> "speed": 0, "type": "mirror", "error": "Operation not permitted"}}
>  {"return": []}
> +{"return": {}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "SHUTDOWN", "data": {"guest": false}}
>  read 65536/65536 bytes at offset 0
>  64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>  {"return": {}}
>  {"return": {}}
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_READY", "data": {"device": "src", "len": 197120, "offset": 197120, 
> "speed": 0, "type": "mirror"}}
>  {"return": [{"io-status": "ok", "device": "src", "busy": false, "len": 
> 197120, "offset": 197120, "paused": false, "speed": 0, "ready": true, "type": 
> "mirror"}]}
> +{"return": {}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "SHUTDOWN", "data": {"guest": false}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 197120, "offset": 
> 197120, "speed": 0, "type": "mirror"}}
>  Warning: Image size mismatch!
>  Images are identical.
>  
> @@ -54,12 +64,17 @@ Specify the 'raw' format explicitly to remove the 
> restrictions.
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
> "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", 

[Qemu-block] [PATCH 1/1] qemu-iotests/109: Fix lock race condition

[Cleber Rosa]

A race condition is currently present between the clean up attempt of
the QEMU process and the execution of qemu-img.  The actual (bad)
output is:

 -Warning: Image size mismatch!
 -Images are identical.
 +qemu-img: Could not open '/tests/qemu-iotests/scratch/t.raw': 
Failed to get "consistent read" lock
 +Is another process using the image?

A KILL signal is sent to the QEMU process, but qemu-img may begin to
run before the QEMU process is really gone.  qemu-img will then
attempt to open the TEST_IMG file before it can secure a lock on it.

This attempts a more graceful shutdown, and waits for the QEMU process
to exit.

Signed-off-by: Cleber Rosa 
---
 tests/qemu-iotests/109 |  3 ++-
 tests/qemu-iotests/109.out | 56 ++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/tests/qemu-iotests/109 b/tests/qemu-iotests/109
index 3b496a3..d70b574 100755
--- a/tests/qemu-iotests/109
+++ b/tests/qemu-iotests/109
@@ -67,7 +67,8 @@ function run_qemu()
 _send_qemu_cmd $QEMU_HANDLE '' "BLOCK_JOB_COMPLETED"
 fi
 _send_qemu_cmd $QEMU_HANDLE '{"execute":"query-block-jobs"}' "return"
-_cleanup_qemu
+_send_qemu_cmd $QEMU_HANDLE '{"execute":"quit"}' "return"
+wait=1 _cleanup_qemu
 }
 
 for fmt in qcow qcow2 qed vdi vmdk vpc; do
diff --git a/tests/qemu-iotests/109.out b/tests/qemu-iotests/109.out
index dc02f9e..c189e28 100644
--- a/tests/qemu-iotests/109.out
+++ b/tests/qemu-iotests/109.out
@@ -12,12 +12,17 @@ Specify the 'raw' format explicitly to remove the 
restrictions.
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": 
"report"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": LEN, "offset": 0, 
"speed": 0, "type": "mirror", "error": "Operation not permitted"}}
 {"return": []}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"SHUTDOWN", "data": {"guest": false}}
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": {}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_READY", "data": {"device": "src", "len": 1024, "offset": 1024, 
"speed": 0, "type": "mirror"}}
 {"return": [{"io-status": "ok", "device": "src", "busy": false, "len": 1024, 
"offset": 1024, "paused": false, "speed": 0, "ready": true, "type": "mirror"}]}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"SHUTDOWN", "data": {"guest": false}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 1024, "offset": 1024, 
"speed": 0, "type": "mirror"}}
 Warning: Image size mismatch!
 Images are identical.
 
@@ -33,12 +38,17 @@ Specify the 'raw' format explicitly to remove the 
restrictions.
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": 
"report"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": LEN, "offset": 512, 
"speed": 0, "type": "mirror", "error": "Operation not permitted"}}
 {"return": []}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"SHUTDOWN", "data": {"guest": false}}
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": {}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_READY", "data": {"device": "src", "len": 197120, "offset": 197120, 
"speed": 0, "type": "mirror"}}
 {"return": [{"io-status": "ok", "device": "src", "busy": false, "len": 197120, 
"offset": 197120, "paused": false, "speed": 0, "ready": true, "type": 
"mirror"}]}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"SHUTDOWN", "data": {"guest": false}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 197120, "offset": 
197120, "speed": 0, "type": "mirror"}}
 Warning: Image size mismatch!
 Images are identical.
 
@@ -54,12 +64,17 @@ Specify the 'raw' format explicitly to remove the 
restrictions.
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": 
"report"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": 
"BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": LEN, "offset": 262144, 
"speed": 0, "type": "mirror", "error": "Operation not permitted"}}
 {"return": []}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP,