Scott Long wrote: > Julian Elischer wrote: >> John Baldwin wrote: >> >>> >>> This is wrong because once you do critical_enter(), you are free to >>> assume that you won't do a context switch until you critical_exit(), >>> and sx_xlock() would violate that if it blocked on the lock. >> >> wellllll critical enter doesn't block interupts so it's true if you >> don't call >> an interrupt as a context switch. >> (it doesn't SWITCH contexts but it does step into a different context.) >> > > Yes, interrupts are serviced when a critical section is entered, but > ithreads are not run on the same CPU until the critical section is > exited. This has been debated quite a bit over the last few years, but > I it's a good compromise. This implications just don't seem to be > documented well, especially for those who need a protected, > uninterruptable context for doing time-critical operations. I think what needs to be documented is a list of "Things thou shalt not do whilst within a FAST interrupt handler". possibly in locking/9 amongst other places. maybe in an interrupts(9) page? > > ScottReceived on Fri May 04 2007 - 20:31:54 UTC
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