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| 1 | <html> | ||
| 2 | <head> | ||
| 3 | <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> | ||
| 4 | <title>2.8.5.7. Stamp Files and the Rerunning of Tasks</title> | ||
| 5 | <link rel="stylesheet" type="text/css" href="../book.css"> | ||
| 6 | <meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> | ||
| 7 | <link rel="home" href="index.html" title="Getting Started With Yocto Project"> | ||
| 8 | <link rel="up" href="bitbake-dev-environment.html" title="2.8.5. BitBake"> | ||
| 9 | <link rel="prev" href="sdk-generation-dev-environment.html" title="2.8.5.6. SDK Generation"> | ||
| 10 | <link rel="next" href="setscene-tasks-and-shared-state.html" title="2.8.5.8. Setscene Tasks and Shared State"> | ||
| 11 | </head> | ||
| 12 | <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="section" title="2.8.5.7. Stamp Files and the Rerunning of Tasks"> | ||
| 13 | <div class="titlepage"><div><div><h4 class="title"> | ||
| 14 | <a name="stamp-files-and-the-rerunning-of-tasks"></a>2.8.5.7. Stamp Files and the Rerunning of Tasks</h4></div></div></div> | ||
| 15 | <p> | ||
| 16 | For each task that completes successfully, BitBake writes a | ||
| 17 | stamp file into the | ||
| 18 | <a class="link" href="../ref-manual/var-STAMPS_DIR.html" target="_self"><code class="filename">STAMPS_DIR</code></a> | ||
| 19 | directory. | ||
| 20 | The beginning of the stamp file's filename is determined by the | ||
| 21 | <a class="link" href="../ref-manual/var-STAMP.html" target="_self"><code class="filename">STAMP</code></a> | ||
| 22 | variable, and the end of the name consists of the task's name | ||
| 23 | and current | ||
| 24 | <a class="link" href="overview-checksums.html" title="3.3.2. Checksums (Signatures)">input checksum</a>. | ||
| 25 | </p> | ||
| 26 | <div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"> | ||
| 27 | <h3 class="title">Note</h3> | ||
| 28 | This naming scheme assumes that | ||
| 29 | <a class="link" href="../bitbake-user-manual/var-BB_SIGNATURE_HANDLER.html" target="_self"><code class="filename">BB_SIGNATURE_HANDLER</code></a> | ||
| 30 | is "OEBasicHash", which is almost always the case in | ||
| 31 | current OpenEmbedded. | ||
| 32 | </div> | ||
| 33 | <p> | ||
| 34 | To determine if a task needs to be rerun, BitBake checks if a | ||
| 35 | stamp file with a matching input checksum exists for the task. | ||
| 36 | If such a stamp file exists, the task's output is assumed to | ||
| 37 | exist and still be valid. | ||
| 38 | If the file does not exist, the task is rerun. | ||
| 39 | </p> | ||
| 40 | <div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"> | ||
| 41 | <h3 class="title">Note</h3> | ||
| 42 | <p>The stamp mechanism is more general than the shared | ||
| 43 | state (sstate) cache mechanism described in the | ||
| 44 | "<a class="link" href="setscene-tasks-and-shared-state.html" title="2.8.5.8. Setscene Tasks and Shared State">Setscene Tasks and Shared State</a>" | ||
| 45 | section. | ||
| 46 | BitBake avoids rerunning any task that has a valid | ||
| 47 | stamp file, not just tasks that can be accelerated through | ||
| 48 | the sstate cache.</p> | ||
| 49 | <p>However, you should realize that stamp files only | ||
| 50 | serve as a marker that some work has been done and that | ||
| 51 | these files do not record task output. | ||
| 52 | The actual task output would usually be somewhere in | ||
| 53 | <a class="link" href="../ref-manual/var-TMPDIR.html" target="_self"><code class="filename">TMPDIR</code></a> | ||
| 54 | (e.g. in some recipe's | ||
| 55 | <a class="link" href="../ref-manual/var-WORKDIR.html" target="_self"><code class="filename">WORKDIR</code></a>.) | ||
| 56 | What the sstate cache mechanism adds is a way to cache task | ||
| 57 | output that can then be shared between build machines. | ||
| 58 | </p> | ||
| 59 | </div> | ||
| 60 | <p> | ||
| 61 | Since <code class="filename">STAMPS_DIR</code> is usually a subdirectory | ||
| 62 | of <code class="filename">TMPDIR</code>, removing | ||
| 63 | <code class="filename">TMPDIR</code> will also remove | ||
| 64 | <code class="filename">STAMPS_DIR</code>, which means tasks will | ||
| 65 | properly be rerun to repopulate <code class="filename">TMPDIR</code>. | ||
| 66 | </p> | ||
| 67 | <p> | ||
| 68 | If you want some task to always be considered "out of date", | ||
| 69 | you can mark it with the | ||
| 70 | <a class="link" href="../bitbake-user-manual/variable-flags.html" target="_self"><code class="filename">nostamp</code></a> | ||
| 71 | varflag. | ||
| 72 | If some other task depends on such a task, then that task will | ||
| 73 | also always be considered out of date, which might not be what | ||
| 74 | you want. | ||
| 75 | </p> | ||
| 76 | <p> | ||
| 77 | For details on how to view information about a task's | ||
| 78 | signature, see the | ||
| 79 | "<a class="link" href="../dev-manual/dev-viewing-task-variable-dependencies.html" target="_self">Viewing Task Variable Dependencies</a>" | ||
| 80 | section in the Yocto Project Development Tasks Manual. | ||
| 81 | </p> | ||
| 82 | </div></body> | ||
| 83 | </html> | ||