On Tue, Jan 21, 2003 at 06:42:25PM -0500, Pierre A. Humblet wrote: >Christopher Faylor wrote: >> >> >> Btw, Pierre, can you explain the rationale behind the "check" parameter >> that some of the internal_* functions take? Why would you not want to >> check for an up-to-date /etc/passwd or /etc/group? > >Two reasons: >1) "check" is only true when the internal functions are called from external >functions. getpwuid and non-reentrant friends return pointers to the malloced >copy. They have to remain valid at least until the next non-reentrant call, >thus cannot be invalidated by refresh from internal lookup functions. >This could be solved with per thread storage, but it's more expensive, >maximum size becomes an issue, etc... >2) internal lookups are used a lot to map uids from/to sids, so decreasing >overhead for them looks like a good idea to make Cygwin faster.
Ok, thanks. >> If not for this, it >> seems like we could get rid of the initialization check entirely and >> just let fn_changed return true when fn[etc_ix] is uninitialized, >> forcing an initial read/parse of the appropriate file. > >That's true for the "uninitialized" state (although it's a cheaper comparison) >but not for the "initializing" state, at least with the current locking >scheme. That condition is checked twice (before and after the mutex), whereas >WaitForSingleEvent and fn_changed normally return false the second time >around even when true the first time. Right, I was changing the locking to occur around the initialization check and then wondered why we needed an initialization check at all. I also used your code/idea to get rid of the state entirely and just check for initialized. cgf
