From: Sergei Slobodov <sergei@slobodov.com>
To: ecos-discuss@sourceware.cygnus.com
Subject: Re: [ECOS] interrupts always enabled in scheduler
Date: Tue, 16 Jan 2001 20:31:00 -0000 [thread overview]
Message-ID: <3A651FEE.2090001@slobodov.com> (raw)
In-Reply-To: <3A64F30F.D5D06970@redhat.com>
Thanks! That makes sense. I assumed that since the config tool allows
configuration with kernel but without DSRs, eCos ISR is allowed to
resume or suspend a thread directly, without resorting to DSR. If this
assumption is wrong, why is including kernel without DSR support not
flagged as a configuration conflict?
Thanks,
Sergei Slobodov
Caracal Consulting Inc.
Jonathan Larmour wrote:
> Sergei Slobodov wrote:
>
>> I'm looking through the sources, trying to determine whether we should
>> try to use ecos or port our own kernel from another platform, and there
>> is at least one major issue I don't understand. ECOS seems to support
>> nested interrupts, yet there is no interrupt enable/disable pair around
>> the code that manipulates thread queues, such as Cyg_Thread::resume(),
>> which non-atomically changes global scheduler structures. Woudn't it
>> cause data corruption if a higher priority interrupt occurs in the
>> middle of resume() call?
>
>
> eCos has been designed to disable interrupts as infrequently as possible.
> No interrupt handler (ISR) will change the thread queues directly. The only
> protection needed is that provided by the scheduler lock ( which is locked
> using Cyg_Scheduler::lock()) which prevents pre-emption by other threads,
> _and_ pre-emption by a deferred service routine (DSR) which is the portion
> of the interrupt handling system which *is* allowed to change the thread
> queues. Only one DSR runs at a time, and these are scheduled outside of
> threads, i.e. no threads run while a DSR runs.
>
> Jifl
next prev parent reply other threads:[~2001-01-16 20:31 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-16 14:45 Sergei Slobodov
2001-01-16 17:19 ` Jonathan Larmour
2001-01-16 20:31 ` Sergei Slobodov [this message]
2001-01-16 23:04 ` Jonathan Larmour
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