user/sven/linux.git/kernel/smp.c, branch v3.4.15

smp: add func to IPI cpus based on parameter func

2012-03-29T00:14:35Z

Add the on_each_cpu_cond() function that wraps on_each_cpu_mask() and calculates the cpumask of cpus to IPI by calling a function supplied as a parameter in order to determine whether to IPI each specific cpu. The function works around allocation failure of cpumask variable in CONFIG_CPUMASK_OFFSTACK=y by itereating over cpus sending an IPI a time via smp_call_function_single(). The function is useful since it allows to seperate the specific code that decided in each case whether to IPI a specific cpu for a specific request from the common boilerplate code of handling creating the mask, handling failures etc. [akpm@linux-foundation.org: s/gfpflags/gfp_flags/] [akpm@linux-foundation.org: avoid double-evaluation of `info' (per Michal), parenthesise evaluation of `cond_func'] [akpm@linux-foundation.org: s/CPU/CPUs, use all 80 cols in comment] Signed-off-by: Gilad Ben-Yossef Cc: Chris Metcalf Cc: Christoph Lameter Acked-by: Peter Zijlstra Cc: Frederic Weisbecker Cc: Russell King Cc: Pekka Enberg Cc: Matt Mackall Cc: Sasha Levin Cc: Rik van Riel Cc: Andi Kleen Cc: Alexander Viro Cc: Avi Kivity Acked-by: Michal Nazarewicz Cc: Kosaki Motohiro Cc: Milton Miller Reviewed-by: "Srivatsa S. Bhat" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

smp: introduce a generic on_each_cpu_mask() function

2012-03-29T00:14:35Z

We have lots of infrastructure in place to partition multi-core systems such that we have a group of CPUs that are dedicated to specific task: cgroups, scheduler and interrupt affinity, and cpuisol= boot parameter. Still, kernel code will at times interrupt all CPUs in the system via IPIs for various needs. These IPIs are useful and cannot be avoided altogether, but in certain cases it is possible to interrupt only specific CPUs that have useful work to do and not the entire system. This patch set, inspired by discussions with Peter Zijlstra and Frederic Weisbecker when testing the nohz task patch set, is a first stab at trying to explore doing this by locating the places where such global IPI calls are being made and turning the global IPI into an IPI for a specific group of CPUs. The purpose of the patch set is to get feedback if this is the right way to go for dealing with this issue and indeed, if the issue is even worth dealing with at all. Based on the feedback from this patch set I plan to offer further patches that address similar issue in other code paths. This patch creates an on_each_cpu_mask() and on_each_cpu_cond() infrastructure API (the former derived from existing arch specific versions in Tile and Arm) and uses them to turn several global IPI invocation to per CPU group invocations. Core kernel: on_each_cpu_mask() calls a function on processors specified by cpumask, which may or may not include the local processor. You must not call this function with disabled interrupts or from a hardware interrupt handler or from a bottom half handler. arch/arm: Note that the generic version is a little different then the Arm one: 1. It has the mask as first parameter 2. It calls the function on the calling CPU with interrupts disabled, but this should be OK since the function is called on the other CPUs with interrupts disabled anyway. arch/tile: The API is the same as the tile private one, but the generic version also calls the function on the with interrupts disabled in UP case This is OK since the function is called on the other CPUs with interrupts disabled. Signed-off-by: Gilad Ben-Yossef Reviewed-by: Christoph Lameter Acked-by: Chris Metcalf Acked-by: Peter Zijlstra Cc: Frederic Weisbecker Cc: Russell King Cc: Pekka Enberg Cc: Matt Mackall Cc: Rik van Riel Cc: Andi Kleen Cc: Sasha Levin Cc: Mel Gorman Cc: Alexander Viro Cc: Avi Kivity Acked-by: Michal Nazarewicz Cc: Kosaki Motohiro Cc: Milton Miller Cc: Russell King Acked-by: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel: Map most files to use export.h instead of module.h

2011-10-31T13:20:12Z

The changed files were only including linux/module.h for the EXPORT_SYMBOL infrastructure, and nothing else. Revector them onto the isolated export header for faster compile times. Nothing to see here but a whole lot of instances of: -#include +#include This commit is only changing the kernel dir; next targets will probably be mm, fs, the arch dirs, etc. Signed-off-by: Paul Gortmaker

generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts

2011-06-17T08:17:12Z

There is a problem that kdump(2nd kernel) sometimes hangs up due to a pending IPI from 1st kernel. Kernel panic occurs because IPI comes before call_single_queue is initialized. To fix the crash, rename init_call_single_data() to call_function_init() and call it in start_kernel() so that call_single_queue can be initialized before enabling interrupts. The details of the crash are: (1) 2nd kernel boots up (2) A pending IPI from 1st kernel comes when irqs are first enabled in start_kernel(). (3) Kernel tries to handle the interrupt, but call_single_queue is not initialized yet at this point. As a result, in the generic_smp_call_function_single_interrupt(), NULL pointer dereference occurs when list_replace_init() tries to access &q->list.next. Therefore this patch changes the name of init_call_single_data() to call_function_init() and calls it before local_irq_enable() in start_kernel(). Signed-off-by: Takao Indoh Reviewed-by: WANG Cong Acked-by: Neil Horman Acked-by: Vivek Goyal Acked-by: Peter Zijlstra Cc: Milton Miller Cc: Jens Axboe Cc: Paul E. McKenney Cc: kexec@lists.infradead.org Link: http://lkml.kernel.org/r/D6CBEE2F420741indou.takao@jp.fujitsu.com Signed-off-by: Ingo Molnar

smp: move smp setup functions to kernel/smp.c

2011-03-23T00:44:11Z

Move setup_nr_cpu_ids(), smp_init() and some other SMP boot parameter setup functions from init/main.c to kenrel/smp.c, saves some #ifdef CONFIG_SMP. Signed-off-by: WANG Cong Cc: Rakib Mullick Cc: David Howells Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Tejun Heo Cc: Arnd Bergmann Cc: Akinobu Mita Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

smp_call_function_interrupt: use typedef and %pf

2011-03-17T23:58:11Z

Use the newly added smp_call_func_t in smp_call_function_interrupt for the func variable, and make the comment above the WARN more assertive and explicit. Also, func is a function pointer and does not need an offset, so use %pf not %pS. Signed-off-by: Milton Miller Signed-off-by: Linus Torvalds

smp_call_function_many: handle concurrent clearing of mask

2011-03-17T23:58:10Z

Mike Galbraith reported finding a lockup ("perma-spin bug") where the cpumask passed to smp_call_function_many was cleared by other cpu(s) while a cpu was preparing its call_data block, resulting in no cpu to clear the last ref and unlock the block. Having cpus clear their bit asynchronously could be useful on a mask of cpus that might have a translation context, or cpus that need a push to complete an rcu window. Instead of adding a BUG_ON and requiring yet another cpumask copy, just detect the race and handle it. Note: arch_send_call_function_ipi_mask must still handle an empty cpumask because the data block is globally visible before the that arch callback is made. And (obviously) there are no guarantees to which cpus are notified if the mask is changed during the call; only cpus that were online and had their mask bit set during the whole call are guaranteed to be called. Reported-by: Mike Galbraith Reported-by: Jan Beulich Acked-by: Jan Beulich Cc: stable@kernel.org Signed-off-by: Milton Miller Signed-off-by: Linus Torvalds

call_function_many: add missing ordering

2011-03-17T23:58:10Z

Paul McKenney's review pointed out two problems with the barriers in the 2.6.38 update to the smp call function many code. First, a barrier that would force the func and info members of data to be visible before their consumption in the interrupt handler was missing. This can be solved by adding a smp_wmb between setting the func and info members and setting setting the cpumask; this will pair with the existing and required smp_rmb ordering the cpumask read before the read of refs. This placement avoids the need a second smp_rmb in the interrupt handler which would be executed on each of the N cpus executing the call request. (I was thinking this barrier was present but was not). Second, the previous write to refs (establishing the zero that we the interrupt handler was testing from all cpus) was performed by a third party cpu. This would invoke transitivity which, as a recient or concurrent addition to memory-barriers.txt now explicitly states, would require a full smp_mb(). However, we know the cpumask will only be set by one cpu (the data owner) and any preivous iteration of the mask would have cleared by the reading cpu. By redundantly writing refs to 0 on the owning cpu before the smp_wmb, the write to refs will follow the same path as the writes that set the cpumask, which in turn allows us to keep the barrier in the interrupt handler a smp_rmb instead of promoting it to a smp_mb (which will be be executed by N cpus for each of the possible M elements on the list). I moved and expanded the comment about our (ab)use of the rcu list primitives for the concurrent walk earlier into this function. I considered moving the first two paragraphs to the queue list head and lock, but felt it would have been too disconected from the code. Cc: Paul McKinney Cc: stable@kernel.org (2.6.32 and later) Signed-off-by: Milton Miller Signed-off-by: Linus Torvalds

call_function_many: fix list delete vs add race

2011-03-17T23:58:10Z

Peter pointed out there was nothing preventing the list_del_rcu in smp_call_function_interrupt from running before the list_add_rcu in smp_call_function_many. Fix this by not setting refs until we have gotten the lock for the list. Take advantage of the wmb in list_add_rcu to save an explicit additional one. I tried to force this race with a udelay before the lock & list_add and by mixing all 64 online cpus with just 3 random cpus in the mask, but was unsuccessful. Still, inspection shows a valid race, and the fix is a extension of the existing protection window in the current code. Cc: stable@kernel.org (v2.6.32 and later) Reported-by: Peter Zijlstra Signed-off-by: Milton Miller Signed-off-by: Linus Torvalds

Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-01-21T02:30:37Z

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: smp: Allow on_each_cpu() to be called while early_boot_irqs_disabled status to init/main.c lockdep: Move early boot local IRQ enable/disable status to init/main.c