| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> |
| |
| <html> |
| |
| <head> |
| <title>monitor-exit</title> |
| <link rel=stylesheet href="opcode.css"> |
| </head> |
| |
| <body> |
| |
| <h1>monitor-exit</h1> |
| |
| <h2>Purpose</h2> |
| |
| <p> |
| Release the monitor for the indicated object. |
| </p> |
| <p> |
| Note: If this instruction needs to throw an exception, it must do so as if the |
| pc has already advanced past the instruction. It may be useful to think of this |
| as the instruction successfully executing (in a sense), and the exception |
| getting thrown after the instruction but before the next one gets a chance to |
| run. This definition makes it possible for a method to use a monitor cleanup |
| catch-all (e.g., finally) block as the monitor cleanup for that block itself, |
| as a way to handle the arbitrary exceptions that might get thrown due to the |
| historical implementation of Thread.stop(), while still managing to have proper |
| monitor hygiene. |
| </p> |
| |
| <h2>Details</h2> |
| |
| <table class="instruc"> |
| <thead> |
| <tr> |
| <th>Op & Format</th> |
| <th>Mnemonic / Syntax</th> |
| <th>Arguments</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td>1e 11x</td> |
| <td>monitor-exit vAA</td> |
| <td><code>A:</code> reference-bearing register (8 bits)</td> |
| </tr> |
| </tbody> |
| </table> |
| |
| <h2>Constraints</h2> |
| |
| <ul> |
| <li> |
| A must be a valid register index for the current stack frame. |
| </li> |
| <li> |
| Register vA must contain a reference to an object. |
| </li> |
| </ul> |
| |
| <h2>Behavior</h2> |
| |
| <ul> |
| <li> |
| An attempt is made for the current thread to release the monitor of the |
| indicated object. |
| </li> |
| <li> |
| If the current thread is the owner, the following happens: |
| <ul> |
| <li> |
| The monitor's entry count is decreased by one. |
| </li> |
| <li> |
| If the entry count has reached zero, the monitor is released. Other |
| threads waiting for the same monitor have a chance to acquire it. |
| </li> |
| </ul> |
| </li> |
| <li> |
| Any exception that gets thrown by this instruction bears the PC of the |
| instruction following the monitor-exit. That is, from the point of view of |
| an exception handler it cannot be distinguished from the same type of |
| exception being thrown immediately after the monitor-exit instruction. |
| </li> |
| </ul> |
| |
| <h2>Exceptions</h2> |
| |
| <ul> |
| <li> |
| NullPointerException is thrown if vA is null. |
| </li> |
| <li> |
| IllegalMonitorStateException is thrown if the current thread is not the |
| owner of that monitor. |
| </li> |
| </ul> |
| |
| </body> |
| </html> |
