user/sven/linux.git/kernel/stop_machine.c, branch v2.6.26.8

stop_machine: make stop_machine_run more virtualization friendly

2008-05-23T03:09:34Z

On kvm I have seen some rare hangs in stop_machine when I used more guest cpus than hosts cpus. e.g. 32 guest cpus on 1 host cpu triggered the hang quite often. I could also reproduce the problem on a 4 way z/VM host with a 64 way guest. It turned out that the guest was consuming all available cpus mostly for spinning on scheduler locks like rq->lock. This is expected as the threads are calling yield all the time. The problem is now, that the host scheduling decisings together with the guest scheduling decisions and spinlocks not being fair managed to create an interesting scenario similar to a live lock. (Sometimes the hang resolved itself after some minutes) Changing stop_machine to yield the cpu to the hypervisor when yielding inside the guest fixed the problem for me. While I am not completely happy with this patch, I think it causes no harm and it really improves the situation for me. I used cpu_relax for yielding to the hypervisor, does that work on all architectures? p.s.: If you want to reproduce the problem, cpu hotplug and kprobes use stop_machine_run and both triggered the problem after some retries. Signed-off-by: Christian Borntraeger CC: Ingo Molnar Signed-off-by: Rusty Russell

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/juhl/trivial

2008-04-21T23:36:46Z

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/juhl/trivial: (24 commits) DOC: A couple corrections and clarifications in USB doc. Generate a slightly more informative error msg for bad HZ fix typo "is" -> "if" in Makefile ext*: spelling fix prefered -> preferred DOCUMENTATION: Use newer DEFINE_SPINLOCK macro in docs. KEYS: Fix the comment to match the file name in rxrpc-type.h. RAID: remove trailing space from printk line DMA engine: typo fixes Remove unused MAX_NODES_SHIFT MAINTAINERS: Clarify access to OCFS2 development mailing list. V4L: Storage class should be before const qualifier (sn9c102) V4L: Storage class should be before const qualifier sonypi: Storage class should be before const qualifier intel_menlow: Storage class should be before const qualifier DVB: Storage class should be before const qualifier arm: Storage class should be before const qualifier ALSA: Storage class should be before const qualifier acpi: Storage class should be before const qualifier firmware_sample_driver.c: fix coding style MAINTAINERS: Add ati_remote2 driver ... Fixed up trivial conflicts in firmware_sample_driver.c

Merge branch 'semaphore' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc

2008-04-21T22:41:27Z

* 'semaphore' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc: Deprecate the asm/semaphore.h files in feature-removal-schedule. Convert asm/semaphore.h users to linux/semaphore.h security: Remove unnecessary inclusions of asm/semaphore.h lib: Remove unnecessary inclusions of asm/semaphore.h kernel: Remove unnecessary inclusions of asm/semaphore.h include: Remove unnecessary inclusions of asm/semaphore.h fs: Remove unnecessary inclusions of asm/semaphore.h drivers: Remove unnecessary inclusions of asm/semaphore.h net: Remove unnecessary inclusions of asm/semaphore.h arch: Remove unnecessary inclusions of asm/semaphore.h

trivial: small cleanups

2008-04-21T22:15:06Z

These are small cleanups all over the tree. Trivial style and comment changes to fs/select.c, kernel/signal.c, kernel/stop_machine.c & mm/pdflush.c Signed-off-by: Pavel Machek Signed-off-by: Jesper Juhl

generic: use new set_cpus_allowed_ptr function

2008-04-19T17:44:58Z

* Use new set_cpus_allowed_ptr() function added by previous patch, which instead of passing the "newly allowed cpus" cpumask_t arg by value, pass it by pointer: -int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask) +int set_cpus_allowed_ptr(struct task_struct *p, const cpumask_t *new_mask) * Modify CPU_MASK_ALL Depends on: [sched-devel]: sched: add new set_cpus_allowed_ptr function Signed-off-by: Mike Travis Signed-off-by: Ingo Molnar

kernel: Remove unnecessary inclusions of asm/semaphore.h

2008-04-19T02:17:04Z

None of these files use any of the functionality promised by asm/semaphore.h. Signed-off-by: Matthew Wilcox

stopmachine: semaphore to mutex

2008-02-06T18:41:08Z

[akpm@linux-foundation.org: cleanup] Signed-off-by: Daniel Walker Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus()

2008-01-25T20:08:02Z

Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use get_online_cpus and put_online_cpus instead as it highlights the refcount semantics in these operations. The new API guarantees protection against the cpu-hotplug operation, but it doesn't guarantee serialized access to any of the local data structures. Hence the changes needs to be reviewed. In case of pseries_add_processor/pseries_remove_processor, use cpu_maps_update_begin()/cpu_maps_update_done() as we're modifying the cpu_present_map there. Signed-off-by: Gautham R Shenoy Signed-off-by: Ingo Molnar

Fix stop_machine_run problem with naughty real time process

2007-07-16T16:05:41Z

stop_machine_run() does its work on "kstopmachine" thread having max priority. However that thread get such priority after woken up. Therefore, in the following case ... - "kstopmachine" try to run on CPU1 - There is a real time process which doesn't relinquish CPU time voluntary on CPU1 ... "kstopmachine" can't start to run and the CPU on which stop_machine_run() is runing hangs up. To fix this problem, call sched_setscheduler() before waking up that thread. Signed-off-by: Satoru Takeuchi Cc: Rusty Russell Cc: Ingo Molnar Cc: Oleg Nesterov Cc: Ashok Raj Cc: Gautham R Shenoy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

stop_machine() now uses hard_irq_disable

2007-05-11T15:29:34Z

Add a call to hard_irq_disable() to stop_machine so that we make sure IRQs are really disabled and not only lazy-disabled on archs like powerpc as some users of stop_machine() may rely on that. [akpm@linux-foundation.org: build fix] Signed-off-by: Benjamin Herrenschmidt Acked-by: Rusty Russell Cc: Paul Mackerras Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds