[gs-bugs] [Bug 692918] New: Concurrency issue....

[bugzilla-daemon at ghostscript.com]

http://bugs.ghostscript.com/show_bug.cgi?id=692918

           Summary: Concurrency issue....
           Product: MuPDF
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P4
         Component: mupdf
        AssignedTo: tor.andersson at artifex.com
        ReportedBy: pedro.rivera.651 at gmail.com
         QAContact: gs-bugs at ghostscript.com


Hi all,

In our multi-thread testing with the latest git commit we came across an issue
(that may not be) but we wanted to ask/inform of our findings.

Here is our test scenario:

(1) Thread #1 => opens document
(2) We then create 4 rendering threads where we submit pages to be rendered in
parallel from document opened in thread #1.
    for (int 1=0; i<pagecount; i++)
      Thread #x => Process page i


The following code causes a crash under this scenario:

fz_try(page->ctx)
{
 page->page = fz_load_page(page->doc->doc, page->page_number-1);
 page->list = fz_new_display_list(page->ctx);
 dev = fz_new_list_device(page->ctx, page->list);
 fz_run_page(page->doc->doc, page->page, dev, fz_identity, NULL);
 page->bbox = fz_bound_page(page->doc->doc, page->page);
}

If we wrap the fz_load_page() and fz_run_page() with a mutex everything works
just fine. This is okay with us but we just wanted to share our findings.

Thanks,

Pedro

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