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From:
kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of richard bravo 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
From:
kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of jiayinjia1983116 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.
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