| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> |
| 2 | |
| 3 | <html> |
| 4 | |
| 5 | <head> |
| 6 | <title>monitor-exit</title> |
| 7 | <link rel=stylesheet href="opcode.css"> |
| 8 | </head> |
| 9 | |
| 10 | <body> |
| 11 | |
| 12 | <h1>monitor-exit</h1> |
| 13 | |
| 14 | <h2>Purpose</h2> |
| 15 | |
| 16 | <p> |
| 17 | Release the monitor for the indicated object. |
| 18 | </p> |
| 19 | <p> |
| 20 | Note: If this instruction needs to throw an exception, it must do so as if the |
| 21 | pc has already advanced past the instruction. It may be useful to think of this |
| 22 | as the instruction successfully executing (in a sense), and the exception |
| 23 | getting thrown after the instruction but before the next one gets a chance to |
| 24 | run. This definition makes it possible for a method to use a monitor cleanup |
| 25 | catch-all (e.g., finally) block as the monitor cleanup for that block itself, |
| 26 | as a way to handle the arbitrary exceptions that might get thrown due to the |
| 27 | historical implementation of Thread.stop(), while still managing to have proper |
| Carl Shapiro | de75089 | 2010-06-08 16:37:12 -0700 | [diff] [blame] | 28 | monitor hygiene. |
| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 29 | </p> |
| 30 | |
| 31 | <h2>Details</h2> |
| 32 | |
| 33 | <table class="instruc"> |
| 34 | <thead> |
| 35 | <tr> |
| 36 | <th>Op & Format</th> |
| 37 | <th>Mnemonic / Syntax</th> |
| 38 | <th>Arguments</th> |
| 39 | </tr> |
| 40 | </thead> |
| 41 | <tbody> |
| 42 | <tr> |
| 43 | <td>1e 11x</td> |
| 44 | <td>monitor-exit vAA</td> |
| 45 | <td><code>A:</code> reference-bearing register (8 bits)</td> |
| 46 | </tr> |
| 47 | </tbody> |
| 48 | </table> |
| 49 | |
| 50 | <h2>Constraints</h2> |
| 51 | |
| 52 | <ul> |
| 53 | <li> |
| 54 | A must be a valid register index for the current stack frame. |
| 55 | </li> |
| 56 | <li> |
| 57 | Register vA must contain a reference to an object. |
| 58 | </li> |
| 59 | </ul> |
| Carl Shapiro | de75089 | 2010-06-08 16:37:12 -0700 | [diff] [blame] | 60 | |
| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 61 | <h2>Behavior</h2> |
| 62 | |
| 63 | <ul> |
| 64 | <li> |
| 65 | An attempt is made for the current thread to release the monitor of the |
| 66 | indicated object. |
| 67 | </li> |
| 68 | <li> |
| 69 | If the current thread is the owner, the following happens: |
| 70 | <ul> |
| 71 | <li> |
| 72 | The monitor's entry count is decreased by one. |
| 73 | </li> |
| 74 | <li> |
| 75 | If the entry count has reached zero, the monitor is released. Other |
| 76 | threads waiting for the same monitor have a chance to acquire it. |
| 77 | </li> |
| 78 | </ul> |
| 79 | </li> |
| 80 | <li> |
| 81 | Any exception that gets thrown by this instruction bears the PC of the |
| 82 | instruction following the monitor-exit. That is, from the point of view of |
| 83 | an exception handler it cannot be distinguished from the same type of |
| 84 | exception being thrown immediately after the monitor-exit instruction. |
| 85 | </li> |
| Carl Shapiro | de75089 | 2010-06-08 16:37:12 -0700 | [diff] [blame] | 86 | </ul> |
| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 87 | |
| 88 | <h2>Exceptions</h2> |
| 89 | |
| 90 | <ul> |
| 91 | <li> |
| 92 | NullPointerException is thrown if vA is null. |
| 93 | </li> |
| 94 | <li> |
| 95 | IllegalMonitorStateException is thrown if the current thread is not the |
| 96 | owner of that monitor. |
| 97 | </li> |
| 98 | </ul> |
| 99 | |
| 100 | </body> |
| 101 | </html> |