Skip to content

L
linux
Switch branch/tag
  1. 31 Jul, 2009 1 commit
    • Shaohua Li's avatar
      ACPI: create Processor Aggregator Device driver · 8e0af514
      Shaohua Li authored 
      ACPI 4.0 created the logical "processor aggregator device" as
a mechinism for platforms to ask the OS to force otherwise busy
processors to enter (power saving) idle.

The intent is to lower power consumption to ride-out
transient electrical and thermal emergencies,
rather than powering off the server.

On platforms that can save more power/performance via P-states,
the platform will first exhaust P-states before forcing idle.
However, the relative benefit of P-states vs. idle states
is platform dependent, and thus this driver need not know
or care about it.

This driver does not use the kernel's CPU hot-plug mechanism
because after the transient emergency is over, the system must
be returned to its normal state, and hotplug would permanently
break both cpusets and binding.

So to force idle, the driver creates a power saving thread.
The scheduler will migrate the thread to the preferred CPU.
The thread has max priority and has SCHED_RR policy,
so it can occupy one CPU.  To save power, the thread will
invoke the deep C-state entry instructions.

To avoid starvation, the thread will sleep 5% of the time
time for every second (current RT scheduler has threshold
to avoid starvation, but if other CPUs are idle,
the CPU can borrow CPU timer from other,
which makes the mechanism not work here)

Vaidyanathan Srinivasan has proposed scheduler enhancements
to allow injecting idle time into the system.  This driver doesn't
depend on those enhancements, but could cut over to them
when they are available.

Peter Z. does not favor upstreaming this driver until
the those scheduler enhancements are in place.  However,
we favor upstreaming this driver now because it is useful
now, and can be enhanced over time.
Signed-off-by: default avatarShaohua Li <shaohua.li@intel.com>
NACKed-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
      8e0af514
  3. 23 Jul, 2009 1 commit
  5. 22 Jul, 2009 37 commits
  7. 21 Jul, 2009 1 commit
    • Trond Myklebust's avatar
      NFSv4: Fix a problem whereby a buggy server can oops the kernel · d953126a
      Trond Myklebust authored 
      We just had a case in which a buggy server occasionally returns the wrong
attributes during an OPEN call. While the client does catch this sort of
condition in nfs4_open_done(), and causes the nfs4_atomic_open() to return
-EISDIR, the logic in nfs_atomic_lookup() is broken, since it causes a
fallback to an ordinary lookup instead of just returning the error.

When the buggy server then returns a regular file for the fallback lookup,
the VFS allows the open, and bad things start to happen, since the open
file doesn't have any associated NFSv4 state.

The fix is firstly to return the EISDIR/ENOTDIR errors immediately, and
secondly to ensure that we are always careful when dereferencing the
nfs_open_context state pointer.
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
      d953126a
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7