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[lwip-devel] [bug #1902] Timeouts and semaphores/mailboxes are too tight


From: Simon Goldschmidt
Subject: [lwip-devel] [bug #1902] Timeouts and semaphores/mailboxes are too tightly integrated
Date: Fri, 09 Mar 2007 08:27:17 +0000
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.8.1.2) Gecko/20070219 Firefox/2.0.0.2

Follow-up Comment #2, bug #1902 (project lwip):

I think this is still a major issue. To solve it means quite a big change in
implementation of the sys layer. Because of this, I'd like comments from
lwip_users, also.

A solution (as discussed e.g. in bug #19167) would be the following:

1. ignore timeouts in semaphore functions since normally, the stack is not in
a condition to let timeout callbacks run if it waits for a sem.

2. timeouts for stack-internal functions may only run in stack context.
initialization should take care of it.

3. IF timeouts for api-threads (like app threads using a socket) are used,
great care must be taken! e.g. timeouts should not run during
sys_mbox_fetch() in netconn_bind(). In other words, the timeout api functions
should NOT be called by a user application. This could best be achieved by
having mboxes allowing timeouts and mboxes not allowing them.

4. To improve timeout accuracy, timestamps should be used. It's still to be
determined if 32-bit timestamps are accurate enough.

Please send your comments, I don't want to change it in the wrong direction.

    _______________________________________________________

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  <http://savannah.nongnu.org/bugs/?1902>

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