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  1. 19 Jun, 2007 5 commits
  3. 18 Jun, 2007 5 commits
    • Linus Torvalds's avatar
      Fix possible runqueue lock starvation in wait_task_inactive() · fa490cfd
      Linus Torvalds authored 
      Miklos Szeredi reported very long pauses (several seconds, sometimes
more) on his T60 (with a Core2Duo) which he managed to track down to
wait_task_inactive()'s open-coded busy-loop.

He observed that an interrupt on one core tries to acquire the
runqueue-lock but does not succeed in doing so for a very long time -
while wait_task_inactive() on the other core loops waiting for the first
core to deschedule a task (which it wont do while spinning in an
interrupt handler).

This rewrites wait_task_inactive() to do all its waiting optimistically
without any locks taken at all, and then just double-check the end
result with the proper runqueue lock held over just a very short
section.  If there were races in the optimistic wait, of a preemption
event scheduled the process away, we simply re-synchronize, and start
over.

So the code now looks like this:

	repeat:
		/* Unlocked, optimistic looping! */
		rq = task_rq(p);
		while (task_running(rq, p))
			cpu_relax();

		/* Get the *real* values */
		rq = task_rq_lock(p, &flags);
		running = task_running(rq, p);
		array = p->array;
		task_rq_unlock(rq, &flags);

		/* Check them.. */
		if (unlikely(running)) {
			cpu_relax();
			goto repeat;
		}

		/* Preempted away? Yield if so.. */
		if (unlikely(array)) {
			yield();
			goto repeat;
		}

Basically, that first "while()" loop is done entirely without any
locking at all (and doesn't check for the case where the target process
might have been preempted away), and so it's possibly "incorrect", but
we don't really care.  Both the runqueue used, and the "task_running()"
check might be the wrong tests, but they won't oops - they just mean
that we could possibly get the wrong results due to lack of locking and
exit the loop early in the case of a race condition.

So once we've exited the loop, we then get the proper (and careful) rq
lock, and check the running/runnable state _safely_.  And if it turns
out that our quick-and-dirty and unsafe loop was wrong after all, we
just go back and try it all again.

(The patch also adds a lot of comments, which is the actual bulk of it
all, to make it more obvious why we can do these things without holding
the locks).

Thanks to Miklos for all the testing and tracking it down.
Tested-by: default avatarMiklos Szeredi <miklos@szeredi.hu>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      fa490cfd
    • Ingo Molnar's avatar
      sched: fix SysRq-N (normalize RT tasks) · a0f98a1c
      Ingo Molnar authored 
      Gene Heskett reported the following problem while testing CFS: SysRq-N
is not always effective in normalizing tasks back to SCHED_OTHER.

The reason for that turns out to be the following bug:

 - normalize_rt_tasks() uses for_each_process() to iterate through all
   tasks in the system.  The problem is, this method does not iterate
   through all tasks, it iterates through all thread groups.

The proper mechanism to enumerate over all threads is to use a
do_each_thread() + while_each_thread() loop.
Reported-by: default avatarGene Heskett <gene.heskett@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a0f98a1c
    • Linus Torvalds's avatar
      Merge master.kernel.org:/pub/scm/linux/kernel/git/jejb/scsi-rc-fixes-2.6 · 4cc21505
      Linus Torvalds authored 
      * master.kernel.org:/pub/scm/linux/kernel/git/jejb/scsi-rc-fixes-2.6:
  [SCSI] ESP: Don't forget to clear ESP_FLAG_RESETTING.
  [SCSI] fusion: fix for BZ 8426 - massive slowdown on SCSI CD/DVD drive
      4cc21505
    • Benjamin Herrenschmidt's avatar
      Fix signalfd interaction with thread-private signals · caec4e8d
      Benjamin Herrenschmidt authored 
      Don't let signalfd dequeue private signals off other threads (in the
case of things like SIGILL or SIGSEGV, trying to do so would result
in undefined behaviour on who actually gets the signal, since they
are force unblocked).
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: default avatarDavide Libenzi <davidel@xmailserver.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      caec4e8d
    • Thomas Gleixner's avatar
      Revert "futex_requeue_pi optimization" · bd197234
      Thomas Gleixner authored 
      This reverts commit d0aa7a70.

It not only introduced user space visible changes to the futex syscall,
it is also non-functional and there is no way to fix it proper before
the 2.6.22 release.

The breakage report ( http://lkml.org/lkml/2007/5/12/17 ) went
unanswered, and unfortunately it turned out that the concept is not
feasible at all.  It violates the rtmutex semantics badly by introducing
a virtual owner, which hacks around the coupling of the user-space
pi_futex and the kernel internal rt_mutex representation.

At the moment the only safe option is to remove it fully as it contains
user-space visible changes to broken kernel code, which we do not want
to expose in the 2.6.22 release.

The patch reverts the original patch mostly 1:1, but contains a couple
of trivial manual cleanups which were necessary due to patches, which
touched the same area of code later.

Verified against the glibc tests and my own PI futex tests.
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Acked-by: default avatarUlrich Drepper <drepper@redhat.com>
Cc: Pierre Peiffer <pierre.peiffer@bull.net>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      bd197234
  5. 17 Jun, 2007 1 commit
  7. 16 Jun, 2007 27 commits
  9. 15 Jun, 2007 2 commits
    • Paul Mundt's avatar
      mm: Fix memory/cpu hotplug section mismatch and oops. · d09c6b80
      Paul Mundt authored 
      When building with memory hotplug enabled and cpu hotplug disabled, we
end up with the following section mismatch:

WARNING: mm/built-in.o(.text+0x4e58): Section mismatch: reference to
.init.text: (between 'free_area_init_node' and '__build_all_zonelists')

This happens as a result of:

        -> free_area_init_node()
          -> free_area_init_core()
            -> zone_pcp_init() <-- all __meminit up to this point
              -> zone_batchsize() <-- marked as __cpuinit                     fo

This happens because CONFIG_HOTPLUG_CPU=n sets __cpuinit to __init, but
CONFIG_MEMORY_HOTPLUG=y unsets __meminit.

Changing zone_batchsize() to __devinit fixes this.

__devinit is the only thing that is common between CONFIG_HOTPLUG_CPU=y and
CONFIG_MEMORY_HOTPLUG=y. In the long run, perhaps this should be moved to
another section identifier completely. Without this, memory hot-add
of offline nodes (via hotadd_new_pgdat()) will oops if CPU hotplug is
not also enabled.
Signed-off-by: default avatarPaul Mundt <lethal@linux-sh.org>
Acked-by: default avatarYasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>

--

 mm/page_alloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
      d09c6b80
    • Linus Torvalds's avatar
      Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/cooloney/blackfin-2.6 · 902233ee
      Linus Torvalds authored 
      * 'master' of master.kernel.org:/pub/scm/linux/kernel/git/cooloney/blackfin-2.6: (30 commits)
  Blackfin SMC91X ethernet supporting driver: SMC91C111 LEDs are note drived in the kernel like in uboot
  Blackfin SPI driver: fix bug SPI DMA incomplete transmission
  Blackfin SPI driver: tweak spi cleanup function to match newer kernel changes
  Blackfin RTC drivers: update MAINTAINERS information
  Blackfin serial driver: decouple PARODD and CMSPAR checking from PARENB
  Blackfin serial driver: actually implement the break_ctl() function
  Blackfin serial driver: ignore framing and parity errors
  Blackfin serial driver: hook up our UARTs STP bit with userspaces CMSPAR
  Blackfin arch: move HI/LO macros into blackfin.h and punt the rest of macros.h as it includes VDSP macros we never use
  Blackfin arch: redo our linker script a bit
  Blackfin arch: make sure we initialize our L1 Data B section properly based on the linked kernel
  Blackfin arch: fix bug can not wakeup from sleep via push buttons
  Blackfin arch: add support for Alon Bar-Lev's dynamic kernel command-line
  Blackfin arch: add missing gpio.h header to fix compiling in some pm configurations
  Blackfin arch: As Mike pointed out range goes form m..MAX_BLACKFIN_GPIO -1
  Blackfin arch: fix spelling typo in output
  Blackfin arch: try to split up functions like this into smaller units according to LKML review
  Blackfin arch: add proper ENDPROC()
  Blackfin arch: move more of our startup code to .init so it can be freed once we are up and running
  Blackfin arch: unify differences between our diff head.S files -- no functional changes
  ...
      902233ee