From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: interrupt context From: Robert Love In-Reply-To: <200304141851.h3EIpZjV015008@sith.maoz.com> References: <200304141851.h3EIpZjV015008@sith.maoz.com> Content-Type: text/plain Message-Id: <1050346609.3664.55.camel@localhost> Mime-Version: 1.0 Date: 14 Apr 2003 14:56:50 -0400 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Jeremy Hall Cc: linux-mm@kvack.org List-ID: On Mon, 2003-04-14 at 14:51, Jeremy Hall wrote: > On a UP machine, is it possible for two interrupts to occur at once? as > in, can card a create an interrupt while card b is in interrupt context? Yes. Normally, all interrupts are enabled (the interrupt system is on) but the _current_ interrupt line is masked out. Thus you will never get a recursive interrupt (A while processing A) but you may get A while processing B. Note if SA_INTERRUPT flag was given to request_irq() then the interrupt is a "fast" interrupt and runs with all interrupts disabled on the local processor. > what about an SMP machine operating in UP mode (nosmp) By nature of above, yes. If you need to ensure concurrency is protected in your interrupt handler, grab a lock and disable interrupts around the critical region. Robert Love -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org