The patch titled
work_on_cpu(): rewrite it to create a kernel thread on demand
has been removed from the -mm tree. Its filename was
work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: work_on_cpu(): rewrite it to create a kernel thread on demand
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
The various implementations and proposed implementations of work_on_cpu()
are vulnerable to various deadlocks because they all use queues of some
form.
Unrelated pieces of kernel code thus gained dependencies wherein if one
work_on_cpu() caller holds a lock which some other work_on_cpu() callback
also takes, the kernel could rarely deadlock.
Also, the present work_on_cpu() implementation creates yet another kernel
thread per CPU.
Fix this by creating a short-lived kernel thread for each work_on_cpu()
invokation.
This is not terribly fast, but the only current caller of work_on_cpu() is
pci_call_probe().
It would be nice to find some other way of doing the node-local
allocations in the PCI probe code so that we can zap work_on_cpu()
altogether. The code there is rather nasty. I can't think of anything
simple at this time...
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)
diff -puN kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand kernel/workqueue.c
--- a/kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand
+++ a/kernel/workqueue.c
@@ -985,20 +985,20 @@ undo:
}
#ifdef CONFIG_SMP
-static struct workqueue_struct *work_on_cpu_wq __read_mostly;
struct work_for_cpu {
- struct work_struct work;
+ struct completion completion;
long (*fn)(void *);
void *arg;
long ret;
};
-static void do_work_for_cpu(struct work_struct *w)
+static int do_work_for_cpu(void *_wfc)
{
- struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);
-
+ struct work_for_cpu *wfc = _wfc;
wfc->ret = wfc->fn(wfc->arg);
+ complete(&wfc->completion);
+ return 0;
}
/**
@@ -1009,17 +1009,23 @@ static void do_work_for_cpu(struct work_
*
* This will return the value @fn returns.
* It is up to the caller to ensure that the cpu doesn't go offline.
+ * The caller must not hold any locks which would prevent @fn from completing.
*/
long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
{
- struct work_for_cpu wfc;
-
- INIT_WORK(&wfc.work, do_work_for_cpu);
- wfc.fn = fn;
- wfc.arg = arg;
- queue_work_on(cpu, work_on_cpu_wq, &wfc.work);
- flush_work(&wfc.work);
-
+ struct task_struct *sub_thread;
+ struct work_for_cpu wfc = {
+ .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
+ .fn = fn,
+ .arg = arg,
+ };
+
+ sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
+ if (IS_ERR(sub_thread))
+ return PTR_ERR(sub_thread);
+ kthread_bind(sub_thread, cpu);
+ wake_up_process(sub_thread);
+ wait_for_completion(&wfc.completion);
return wfc.ret;
}
EXPORT_SYMBOL_GPL(work_on_cpu);
@@ -1035,8 +1041,4 @@ void __init init_workqueues(void)
hotcpu_notifier(workqueue_cpu_callback, 0);
keventd_wq = create_workqueue("events");
BUG_ON(!keventd_wq);
-#ifdef CONFIG_SMP
- work_on_cpu_wq = create_workqueue("work_on_cpu");
- BUG_ON(!work_on_cpu_wq);
-#endif
}
_
Patches currently in -mm which might be from akpm@xxxxxxxxxxxxxxxxxxxx are
i-need-old-gcc.patch
i2c-too-much-compiler-noise.patch
linux-next.patch
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git-acpi-vs-git-cpufreq.patch
thinkpad-acpi-split-delayed-leds-stuff-clean-up-code.patch
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early-platform-driver-v3.patch
sysfs-dont-block-indefinitely-for-unmapped-files.patch
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clocksource-pass-clocksource-to-read-callback.patch
input-bcm5974-declare-alignment-usage.patch
input-keyboard-introduce-lm8323-driver.patch
drivers-input-xpadc-improve-xbox-360-wireless-support-and-add-sysfs-interface-checkpatch-fixes.patch
input-documentation-input-xpadtxt-update-for-new-driver-functionality-checkpatch-fixes.patch
leds-add-bd2802gu-led-driver.patch
mmc-add-extended-csd-register-to-debugfs.patch
mtd-rbtx4939-add-mtd-support.patch
mtd-flex-onenand-support-fix.patch
misdn-l1oip-reduce-stack-memory-footprint.patch
drivers-net-82596c-suppress-warnings.patch
pci-quirks-unhide-overflow-device-on-i828675p-pe-chipsets-v2-checkpatch-fixes.patch
raw-fix-rawctl-compat-ioctls-breakage-on-amd64-and-itanic.patch
vfs-simple_set_mnt-should-return-void.patch
libfs-make-simple_read_from_buffer-conventional-fix.patch
__tty_open-use-the-correct-type-for-saved_flags.patch
mtd_dataflash-fix-probing-of-at45db321c-chips-checkpatch-fixes.patch
scsi-dpt_i2o-is-bust-on-ia64.patch
ia64-fix-pci-dma-flag-propagation-on-sn-altix-with-pics.patch
input-add-a-dmi-table-for-the-i8042reset-option-make-msi-wind-u-100-work.patch
nommu-fix-a-number-of-issues-with-the-per-mm-vma-patch.patch
page_fault-retry-with-nopage_retry.patch
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page_fault-retry-with-nopage_retry-fix-fix.patch
mm-add-proc-controls-for-pdflush-threads-fix.patch
mm-add-proc-controls-for-pdflush-threads-fix-fix.patch
mm-add-proc-controls-for-pdflush-threads-fix-99.patch
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do_pipe-drop-its-last-user-in-arch-alpha-checkpatch-fixes.patch
alpha-convert-u64-to-unsigned-long-long-fix.patch
alpha-convert-u64-to-unsigned-long-long-fix-2.patch
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rtc-test-before-subtraction-on-unsigned-fix.patch
drivers-video-uvesafbc-dont-use-gfp_any.patch
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cirrusfb-convert-printks-to-dev_foo-fix-fix2.patch
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