RE: Spinlocks on Uniprocessor

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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 <rajendra.stalekar@xxxxxxxxx> wrote:
 
 

From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of jiayinjia1983116
Sent: Thursday, September 20, 2007 11:06 AM
To: Mansha Linux
Cc: kernelnewbies@xxxxxxxxxxxx
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" <mansha.linux@xxxxxxxxx> £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



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