On 24 Feb, John Baldwin wrote: > On Tuesday 24 February 2004 10:52 am, Don Lewis wrote: >> On 24 Feb, John Baldwin wrote: >> > Eek, why not a sx lock if you must go to a sleepable lock? >> >> That was my initial thought, but I was scared off by the following >> statement in the sx(9) man page: >> >> A thread may not own a shared lock and an exclusive lock >> simultaneously; attempting to do so will result in deadlock. >> >> My plan is to hold this lock across large portions of the open() and >> ioctl() methods (and possibly read() and write() as well). Some of >> these may call code outside of my direct control, such as methods in the >> hardware specific drivers, as well as things like malloc(). I'm >> concerned about causing a deadlock by violating the sx usage rules. > > It means on the same lock, i.e. you can't try to do sx_slock(&foo) and then do > sx_xlock(&foo). You can mix shared/exclusive of different locks ok. Cool! I'll make it an sx lock. The man page should probably be clarified, maybe something like: A thread must not attempt to acquire a lock both shared and exclusive at the same time. Such an attempt will result in a deadlock.Received on Tue Feb 24 2004 - 07:11:45 UTC
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