[lwip-users] FW: [lwip-devel] [bug #1902] Timeouts and semaphores/mailboxes are tootightly integrated

[Goldschmidt Simon]

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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