Messages in this thread | | | Date | Sun, 31 May 1998 14:54:19 +0200 (CEST) | From | Andrea Arcangeli <> | Subject | Re: test_and_set_bit() not atomic forever? [cli/sti in char/vt.c [patch]] |
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On Sun, 31 May 1998, Mike Ford Ditto wrote:
>There seems to be some terminology confusion here. There are two kinds >of atomicicty... many CPUs provide an "atomic" test-and-set instruction >which can not be interrupted (by interrupts, that is). These >instructions usually are not atomic at the bus level, only at the CPU >instruction level. Another bus master (a DMA device or another CPU) can >access the same memory word inbetween the test and the set.
This is _not_ the needed atomicity for test_and_set_bit() I think...
>So another kind of atomicity is often provided which is guaranteed >atomic even against other CPUs contending for the same word using the
I think this is the right atomicity for test_and_set_bit() (and i386 implement it in this way). Probably all ports are implementing test_and_set_bit() in this way too just now so I think this is no more an issue.
Andrea[s] Arcangeli
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