[haiku-gsoc] Re: Implementation Queries

  • From: Hamish Morrison <hamishm53@xxxxxxxxx>
  • To: haiku-gsoc@xxxxxxxxxxxxx
  • Date: Sun, 18 Jun 2017 13:07:17 +0100

On 18/06/2017 11:34, Vivek Roy wrote:

    That one implements a normal mutex, FreeBSD's sx is short for
    shared/exclusive-lock, another name for a read/write-lock. According
    to [0] they have a few specialties regarding their scheduling. You
    could try and implement them using the Haiku kernel's rw_lock (see
    headers/private/shared/locks.h), although it might be necessary to
    take a close look at differences in behaviour. Also, our rw_lock
    doesn't implement all the functions of FreeBSD's sx, such as
    try-to-lock, so it needs to be seen of those are being used in the
    code you're compiling.

    [0] https://www.freebsd.org/cgi/man.cgi?query=sx_slock&sektion=9
    <https://www.freebsd.org/cgi/man.cgi?query=sx_slock&sektion=9>


Okay, trying to implement sx.

Thanks

There's no reason to use a read/write lock here. All that linux/mutex.h provides is a simple mutex, not a read/write lock. Just because FreeBSD have chosen to implement this with a rwlock doesn't mean we need to do the same. We can just implement this with a regular mutex.

You can use the mutex from here to implement it:

http://cgit.haiku-os.org/haiku/tree/headers/private/kernel/lock.h

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