View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0002085 | libmicrohttpd | external even loop | public | 2012-01-19 14:38 | 2012-01-23 13:21 |
| Reporter | tclaveirole | Assigned To | Christian Grothoff | Due Date | |
| Priority | normal | Severity | minor | Reproducibility | sometimes |
| Status | closed | Resolution | fixed | ||
| Product Version | 0.9.17 | ||||
| Target Version | 0.9.18 | Fixed in Version | 0.9.18 | ||
| Summary | 0002085: MHD_get_timeout relies on uninitialized variable, leads to busy waiting sometimes | ||||
| Description | The earliest_deadline variable in MHD_get_timeout (src/daemon/daemon.c, line 1204) is not initialized. Therefore, the comparison on line 1223 is invalid. On some occasions (e.g., earliest_deadline's first value is zero), this leads to returning an incorrect timeout. Sometimes this incorrect timeout is constantly zero and the HTTP server starts busy waiting. | ||||
| Steps To Reproduce | Because this bug depends on the state of an uninitialized variable, it is sometimes hard to reproduce. Here are steps that triggers the bug every time on my machine (Debian i386 testing, with Debian GCC 4.6.2-11). 1. Use a libmicrohttpd that has optimizations disabled (i.e., compiled with -O0. Else the uninitialized variable goes into a register and the result is unpredictable). 2. Compile and run the attached test.c. This is a simple HTTP server that uses libmicrohttpd with external select and connection timeouts. Each time MHD_get_timeout returns a valid timeout with value 0, the server prints a '.' character. The server never replies to requests (so it should close HTTP connections abruptly when their timeouts expire). 3. Make a request to the server. The server then busy waits: it prints a lot of '.' until the timeout is reached and the connection closed. At this point, it goes back to using select() with no timeout. This is not the expected behavior. As nothing is done to reply to the request, the server should have spent most of its time blocked in select() with a proper timeout. | ||||
| Additional Information | Attached is a patch that solves that bug. | ||||
| Tags | No tags attached. | ||||
| Attached Files | |||||
| related to | 0002018 | closed | Christian Grothoff | GNUnet | http(s) transport eats cpu |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2012-01-19 14:38 | tclaveirole | New Issue | |
| 2012-01-19 14:38 | tclaveirole | File Added: attachments.tar | |
| 2012-01-19 16:33 | Christian Grothoff | Target Version | => 0.9.18 |
| 2012-01-19 16:34 | Christian Grothoff | Assigned To | => Christian Grothoff |
| 2012-01-19 16:34 | Christian Grothoff | Status | new => assigned |
| 2012-01-19 16:47 | Christian Grothoff | Note Added: 0005296 | |
| 2012-01-19 16:47 | Christian Grothoff | Status | assigned => resolved |
| 2012-01-19 16:47 | Christian Grothoff | Fixed in Version | => 0.9.18 |
| 2012-01-19 16:47 | Christian Grothoff | Resolution | open => fixed |
| 2012-01-19 21:21 | Christian Grothoff | Relationship added | related to 0002018 |
| 2012-01-23 13:21 | Christian Grothoff | Status | resolved => closed |
| 2013-05-06 10:52 | Christian Grothoff | Category | external select => libmicrohttpd external select |
| 2024-01-21 12:24 | Christian Grothoff | Category | libmicrohttpd external select => external even loop |