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authorZachary Amsden <zach@vmware.com>2006-12-15 01:38:04 +0100
committerAdrian Bunk <bunk@stusta.de>2006-12-15 01:38:04 +0100
commite89da8fc50c416abf4abab77d851e051df0edbec (patch)
tree35a87483bd9c3d09c9cab77b29534245528915d7 /kernel
parenta26b7719f9bde7e74385bfa6ca3ea89d365efd77 (diff)
softirq: remove BUG_ONs which can incorrectly trigger
It is possible to have tasklets get scheduled before softirqd has had a chance to spawn on all CPUs. This is totally harmless; after success during action CPU_UP_PREPARE, action CPU_ONLINE will be called, which immediately wakes softirqd on the appropriate CPU to process the already pending tasklets. So there is no danger of having a missed wakeup for any tasklets that were already pending. In particular, i386 is affected by this during startup, and is visible when using a very large initrd; during the time it takes for the initrd to be decompressed, a timer IRQ can come in and schedule RCU callbacks. It is also possible that resending of a hardware IRQ via a softirq triggers the same bug. Because of different timing conditions, this shows up in all emulators and virtual machines tested, including Xen, VMware, Virtual PC, and Qemu. It is also possible to trigger on native hardware with a large enough initrd, although I don't have a reliable case demonstrating that. Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Adrian Bunk <bunk@stusta.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/softirq.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c
index ad3295cdded5..6abbc724495f 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -454,8 +454,6 @@ static int __devinit cpu_callback(struct notifier_block *nfb,
switch (action) {
case CPU_UP_PREPARE:
- BUG_ON(per_cpu(tasklet_vec, hotcpu).list);
- BUG_ON(per_cpu(tasklet_hi_vec, hotcpu).list);
p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu);
if (IS_ERR(p)) {
printk("ksoftirqd for %i failed\n", hotcpu);