[asterisk-dev] [Code Review] Make ast_unload_resource actually remove the module from the module list when it is unloaded

[Terry Wilson]

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This is an automatically generated e-mail. To reply, visit:
https://reviewboard.asterisk.org/r/1752/
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(Updated Feb. 22, 2012, 12:12 p.m.)


Review request for Asterisk Developers.


Changes
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Use tilghman's suggestion of using module usecount. There is no reason that passing NULL for the channel should be a problem, since struct ast_module_user is opaque outside of loader.c and ->chan is only used for the hangup. This patch wraps the softhangup in a if (u->chan) in ast_module, then calls ast_module_user_add/remove when registering/unregistering channel techs. Crashing for 'core stop gracefully' then goes away.


Summary
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res_calendar calls ast_unload_resource for the related tech modules when it is unloaded. If this happens through a 'core stop gracefully', then it will be unloading the tech modules that are already in the list that is being traversed (supposedly safely) for unloading, eventually causing a double free. The problem seems to be that ast_unload_resource, while it calls the unload() callback function for the module, does not actually unlink the module from the list of modules. So the AST_LIST_TRAVERSE_SAFE_BEGIN {} still iterates over the unloaded module.

This patch causes ast_unload_resource to call AST_LIST_REMOVE on successfully unloaded modules.


Diffs (updated)
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  /trunk/include/asterisk/calendar.h 356213 
  /trunk/main/loader.c 356213 
  /trunk/res/res_calendar.c 356213 

Diff: https://reviewboard.asterisk.org/r/1752/diff


Testing
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Scenario: Start Asterisk with res_calendar and assorted calendar tech modules loaded. Run 'core stop gracefully'.
Before patch: Crash.
After patch: No crash.


Thanks,

Terry

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