linux-kernel - RE: Clarification required about select vs wake

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Message-ID: <FA6FB5FA4DA6BF4386D129273B2E3EC30183A419@xmb-sjc-214.amer.cisco.com>
Date:	Wed, 14 Mar 2007 09:33:41 -0700
From:	"Ravinandan Arakali \(rarakali\)" <rarakali@...co.com>
To:	"Arjan van de Ven" <arjan@...radead.org>
Cc:	<linux-kernel@...r.kernel.org>
Subject: RE: Clarification required about select vs wake_up race condition

Hi,
Our driver is not in the kernel tree yet.
The code snippet from poll entry point is as follows:

    mask = 0;
    poll_wait(filp, &(sap_desc->recv_any_wq), poll_table);
    /* We don't have yet a waiting queue for writers... */
    lock_mts();
    if ((sap_desc->recv_q.first != NULL) &&
        (block_ssync_event(sap_desc->recv_q.first) == FALSE)) {
        /* The queue can be read. */
        mask |= POLLIN | POLLRDNORM;
    }
    unlock_mts();
    //MTS_HOOK(mts_syscall_exit,__FUNCTION__,mask);
    return mask; 

The wake_up_interruptible(&(sap_desc->recv_any_wq)) is executed
from the sending process.

Hope this is sufficient. As I mentioned in my previous mail, what I
am trying to understand better is the kernel code path of do_select() 
versus wake_up_interruptible.

Thanks,
Ravi

-----Original Message-----
From: Arjan van de Ven [mailto:arjan@...radead.org] 
Sent: Wednesday, March 14, 2007 4:08 AM
To: Ravinandan Arakali (rarakali)
Cc: linux-kernel@...r.kernel.org
Subject: Re: Clarification required about select vs wake_up race
condition

On Mon, 2007-03-12 at 12:44 -0700, Ravinandan Arakali (rarakali) wrote:
> Hi,
> I am facing following problem and was wondering if somebody could help

> me out.
> Our char driver(pretty much like all other char drivers) does a
> poll_wait()

you forgot to include your (full) sourcecode or a pointer to that...
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