From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of richard bravo Sent: Friday, September 21, 2007 3:15 PM To: Rajendra Stalekar; 'jiayinjia1983116'; 'Mansha Linux' Cc: [email protected] Subject: RE: Spinlocks on Uniprocessor
In UP machines Spinlocks are compiled away, so that it only disables interrupts on spin_lock_irqsave and enables interrupts on spin_lock_irqrestore. This protects the critical section the code executing in process context and interrupt routine. Pls correct me if I am wrong. [rajendra stalekar] AFAIK, spinlocks anyway disable interrupts, however, once it gets unlocked it enables it. The reason why we call spin_lock_irqsave could be that , if the interrupt did comes by, it would be kept pending and then once it i.e. spin_lock_irqrestore , it will invoke the interrupt handler. Please let me know if I am right on this Rajendra Stalekar <[EMAIL PROTECTED]> wrote: _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of jiayinjia1983116 Sent: Thursday, September 20, 2007 11:06 AM To: Mansha Linux Cc: [email protected] Subject: Re:Spinlocks on Uniprocessor As for as I know,when process/Thread is in runqueue,then may have allocate some resource even they do not running right now,In order to keep the data consistent(can not be modified by other processes/threads) ,we should use spinlock to protect the data. [rajendra stalekar] > I think that the code protected by spinlock must never have a blocking call(eg. copy_to_user, copy_from_user, read, write etc), whenever a thread acquires a spinlock whatever the critical section code has to be asynchronous and yes of course kernel must be pre-emptible. ÔÚ2007-09-19£¬"Mansha Linux" <[EMAIL PROTECTED]> £º Hi all, Could you please explain me why do we need the spinlocks on uniprocessor machines? Is this the only reason that the kernel is preemptive ? -- regards, Mansha _____ ɱ70ÍòÖÖľÂí²¡¶¾£¬ <http://pro.163.com/event.ng/Type=click&FlightID=96648&AdID=98138&TargetID=6 35&Values=31,43,51,60,72,82,91,100,110,312,330,332,499,587,702,733,734&Redir ect=http:/ad.cn.doubleclick.net/clk;134682177;20226578;k%3Fhttp:/www.rising. com.cn/2008/trial/index.htm> ÈðÐÇ2008°æÃâ·Ñ http://www.patni.com <http://www.patni.com/> World-Wide Partnerships. World-Class Solutions. _____________________________________________________________________ This e-mail message may contain proprietary, confidential or legally privileged information for the sole use of the person or entity to whom this message was originally addressed. Any review, e-transmission dissemination or other use of or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you have received this e-mail in error kindly delete this e-mail from your records. If it appears that this mail has been forwarded to you without proper authority, please notify us immediately at [EMAIL PROTECTED] and delete this mail. _____________________________________________________________________ _____ Tonight's top picks. What will you watch tonight? Preview <http://us.rd.yahoo.com/tv/mail/tagline/tonightspicks/evt=48220/*http:/tv.ya hoo.com/%20%0d%0a> the hottest shows on Yahoo! TV. http://www.patni.com World-Wide Partnerships. World-Class Solutions. _____________________________________________________________________ This e-mail message may contain proprietary, confidential or legally privileged information for the sole use of the person or entity to whom this message was originally addressed. Any review, e-transmission dissemination or other use of or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you have received this e-mail in error kindly delete this e-mail from your records. If it appears that this mail has been forwarded to you without proper authority, please notify us immediately at [EMAIL PROTECTED] and delete this mail. _____________________________________________________________________
