unpigz -l failed with "can't destroy locked resource"

[wrjiafang]

Create a file about 200M size named test.txt and pigz this file to get test.txt.gz and then "unpigz -l" will failed, error as:
$ ./unpigz -l test.txt.gz
compressed original reduced name
228799 209715200 99.9% test.txt
unpigz: can't destroy locked resource (pigz.c:2622:mutex_destroy)
unpigz: abort: internal threads error

or

$ ./unpigz -l test.txt.gz
unpigz: skipping: test.txt.gz unrecognized format
unpigz: can't destroy locked resource (pigz.c:2622:mutex_destroy)
unpigz: abort: internal threads error

It seems like there are data race when use valgrind tool to check.
We found that, "unpigz" will g.decode = 1; and then in process(), use in_init(); method = get_header(1);
However, the following g.list, list_info(), will also in_init();method = get_header(1);
This will lead to get_header()-->GET()-->load()-->
if (g.procs > 1) {
// if first time, fire up the read thread, ask for a read
if (g.in_which == -1) {
g.in_which = 1;
g.load_state = new_lock(1);
g.load_thread = launch(load_read, NULL);
}
Double init g.load_state and create load_read thread.
Then there are many data race and the thread will be failed to destroy with error (EBUSY: Device or resource busy)

[wrjiafang]

To avoid the double init and create thread, but get the correct method value. We can fix it by:

+    
+       // if requested, just list information about input file
+    if (g.list) {
+        list_info();
+        load_end();
+        return;
+    }

     // if decoding or testing, try to read gzip header
     if (g.decode) {
@@ -4048,13 +4055,6 @@
         }
     }

-    // if requested, just list information about input file
-    if (g.list) {
-        list_info();
-        load_end();
-        return;
-    }
-

Put the list_info before any decode, since it does not make sense to do any decode job if just list info.
Please give some suggestions. Thanks.
.

[madler]

Thank you for the report. Actually, it does make sense to decode for listing, for pigz -lt. However I did not consider the possibility of what you're requesting, which is equivalent to pigz -ld. The fix is similar to your proposal, but adding a check on g.decode:

@@ -4021,6 +4021,13 @@ local void process(char *path) {
     }
     SET_BINARY_MODE(g.ind);
 
+    // if requested, just list information about the input file
+    if (g.list && g.decode != 2) {
+        list_info();
+        load_end();
+        return;
+    }
+
     // if decoding or testing, try to read gzip header
     if (g.decode) {
         in_init();
@@ -4062,13 +4069,6 @@ local void process(char *path) {
         }
     }
 
-    // if requested, just list information about input file
-    if (g.list) {
-        list_info();
-        load_end();
-        return;
-    }
-
     // create output file out, descriptor outd
     if (path == NULL || g.pipeout) {
         // write to stdout

This will be updated in a future version.

[wrjiafang]

@madler Thanks very much for your quick reply. Understood, let's look forward to your new version.