Messages in this thread | | | From | "Luck, Tony" <> | Date | Fri, 29 May 2009 09:13:10 -0700 | Subject | RE: [perfmon2] comments on Performance Counters for Linux (PCL) |
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>> Happen to have more details? If they really run in user context their >> priv level would be the same right, otherwise they run in something >> weird, not quite user not quite kernel. Now that might be the case, but >> I'm utterly ignorant on itanic. > > See Documentation/ia64/fsys.txt
Summary is that the fast system calls run in ring 0 ... but since they didn't save all the user state (in order to make them fast!) there are restrictions on what things they can do. In particular they must not trap.
-Tony
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