Messages in this thread |  | | | Date | Sat, 05 Nov 2005 10:18:17 +0900 | | From | Tejun Heo <> | | Subject | Re: [PATCH RFC] big reader semaphore take#2 |
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Nick Piggin wrote: > Tejun Heo wrote: > >> Tejun Heo wrote: >> >>> Hello guys, >>> >>> This is the second take of brsem (big reader semaphore). >>> >>> Nick, unfortunately, simple array of rwsem's does not work as lock >>> holders are not pinned down to cpus and may release locks on other >>> cpus. >>> > > [...] > >> >> (Nick, what do you think about the new implementation?) >> > > As I said, I think I'd prefer to see an implementation that returns > a token from down_read to be used in up_read (ie. the slot # of the > counter which has been downed). >
Oh... I read your response but thought that was only response to 'that wouldn't work' part.
> This obviously no longer makes it a drop in replacement for an rwsem. > But could such a beast ever be considered so? Would that make your > VFS patches really ugly?
I think Al Viro is on that now.
> The upshot of that would be that you could build the whole thing > from rwsem infrastructure and have basically zero other locking > mechanisms or complexity that you don't want in a synchronisation > primitive. >
To certain extent, I do agree with you - it's safer/simpler..., but on the other hand, new brsem isn't that more complex and would perform almost identically without extra semantical baggage. So, I thought it might be worth a bit more effort.
Hmm... So, array of rwsem's, it should be.
Thanks.
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