Re: [git pull] scheduler fixes

[Matthew Wilcox]

On Sun, May 11, 2008 at 05:03:06AM -0600, Matthew Wilcox wrote:
> This might be the problem that causes the missing wakeups.  If you have a
> semaphore with n=2, and four processes calling down(), tasks A and B
> acquire the semaphore and tasks C and D go to sleep.  Task A calls up()
> and wakes up C.  Then task B calls up() and doesn't wake up anyone
> because C hasn't run yet.  I think we need another wakeup when task C

Er, I mis-wrote there.

Task A calls up() and wakes up C.  Then task B calls up() and wakes up C
again because C hasn't removed itself from the list yet.  D never
receives a wakeup.  The solution is for C to pass a wakeup along to the
next in line.  (The solution remains the same).

-- 
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operating system, but compare it to ours.  We can't possibly take such
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