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    SubjectRe: [linux-usb-devel] Re: [PATCH 00/10] usb-serial: Switches from spin lock to atomic_t.
    Date
    Am Dienstag, 6. Dezember 2005 22:18 schrieb Luiz Fernando Capitulino:
    >
    > Hi Pete,
    >
    > On Tue, 6 Dec 2005 13:02:07 -0800
    > Pete Zaitcev <zaitcev@redhat.com> wrote:
    >
    > | On Tue, 6 Dec 2005 18:14:49 -0200, Luiz Fernando Capitulino <lcapitulino@mandriva.com.br> wrote:
    > |
    > | > The spinlock makes the code less clear, error prone, and we already a
    > | > semaphore in the struct usb_serial_port.
    > | >
    > | > The spinlocks _seems_ useless to me.
    > |
    > | Dude, semaphores are not compatible with interrupts. Surely you
    > | understand that?
    >
    > Sure thing man, take a look at this thread:
    >
    > http://marc.theaimsgroup.com/?l=linux-kernel&m=113216151918308&w=2
    >
    > My comment 'we already have a semaphore in struct usb_serial_port'
    > was about what we've discussed in that thread, where question like
    > 'why should we have yet another lock here?' have been made.
    >
    > And *not* 'let's use the semaphore instead'.
    >
    > If _speed_ does not make difference, the spinlock seems useless,
    > because we could use atomic_t instead.

    You can atomically set _one_ value using atomic_t. A spinlock allows
    that and other more complex schemes.

    Regards
    Oliver
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