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problem with select()
- From: Маврин Геннадий <genamavr at mail dot ru>
- To: ecos-discuss at ecos dot sourceware dot org
- Date: Sun, 02 Apr 2006 19:01:15 +0400
- Subject: [ECOS] problem with select()
- Reply-to: Маврин Геннадий <genamavr at mail dot ru>
I use the old version of ecos (ecos 2.0 downloaded at December 2003). But I searched the problem I have in the ecos bug tracking database and didn't find it.
I use select() function to wait when the descriptor will be ready for reading. Sometime select() returns 0 (time limit expire) but I am sure that the requested descriptor was ready for reading some time ago. After that if I perform the reading operation with this descriptor it completes successfully.
I think that I know the reason of this problem. The structure of cyg_pselect() function is:
int cyg_pselect( )
{
while (!error)
{
for (mode = 0; !error && mode < 3; mode++)
{
...
// Checking the descriptors to be ready to requested operation
...
}
...
Cyg_Scheduler::lock();
...
// Waiting for cyg_selwakeup() call
...
Cyg_Scheduler::unlock();
}
}
I think that the descriptor may come ready after the loop which checks the descriptors to be ready to requested operation but before Cyg_Scheduler::lock() function call. In this case cyg_pselect( ) will wait for descriptor even if this descriptor is ready. My idea is to move Cyg_Scheduler::lock() call up.
int cyg_pselect( )
{
while (!error)
{
for (mode = 0; !error && mode < 3; mode++)
{
Cyg_Scheduler::lock();
...
// Checking the descriptors to be ready to requested operation
...
}
...
// Waiting for cyg_selwakeup() call
...
Cyg_Scheduler::unlock();
}
}
Is my idea good or not?
Gennady
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