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Subject[BUG -rt] scheduling in atomic.

I've hit this. I compiled the kernel as CONFIG_PREEMPT, and turned off
IRQ's as threads.

BUG: scheduling while atomic: swapper/0x00000001/1, CPU#3

Call Trace:
[<ffffffff8026f9b0>] dump_trace+0xaa/0x404
[<ffffffff8026fd46>] show_trace+0x3c/0x52
[<ffffffff8026fd71>] dump_stack+0x15/0x17
[<ffffffff8026562a>] __sched_text_start+0x8a/0xbb7
[<ffffffff80266492>] schedule+0xd3/0xf3
[<ffffffff802a11bd>] flush_cpu_workqueue+0x72/0xa4
[<ffffffff802a125c>] flush_workqueue+0x6d/0x95
[<ffffffff802a19a8>] schedule_on_each_cpu+0xe8/0xff
[<ffffffff802dc927>] filevec_add_drain_all+0x12/0x14
[<ffffffff80304701>] remove_proc_entry+0xaf/0x258
[<ffffffff802c1782>] unregister_handler_proc+0x23/0x48
[<ffffffff802bff91>] free_irq+0xda/0x114
[<ffffffff803fe3fa>] i8042_probe+0x338/0x75c
[<ffffffff803ba4b1>] platform_drv_probe+0x12/0x14
[<ffffffff803b8b00>] really_probe+0x54/0xee
[<ffffffff803b8c48>] driver_probe_device+0xae/0xba
[<ffffffff803b8c5d>] __device_attach+0x9/0xb
[<ffffffff803b7ef8>] bus_for_each_drv+0x47/0x7d
[<ffffffff803b8cc4>] device_attach+0x65/0x79
[<ffffffff803b7e89>] bus_attach_device+0x24/0x4c
[<ffffffff803b6f7d>] device_add+0x38f/0x505
[<ffffffff803ba7ca>] platform_device_add+0x11a/0x152
[<ffffffff808e1d1f>] i8042_init+0x2b0/0x30d
[<ffffffff8026ea53>] init+0x182/0x344
[<ffffffff80261f08>] child_rip+0xa/0x12

Seems that we have this in remove_proc_entry:

for (p = &parent->subdir; *p; p=&(*p)->next ) {





And in proc_kill_inodes:

static void proc_kill_inodes(struct proc_dir_entry *de)
struct file *filp;
struct super_block *sb = proc_mnt->mnt_sb;

* Actually it's a partial revoke().


and in filevec_add_drain_all:

int filevec_add_drain_all(void)
return schedule_on_each_cpu(filevec_add_drain_per_cpu, NULL);

And schedule_on_each_cpu is easily schedulable.

So it seems that it schedules while holding a spin lock.

I don't know this code very well, and don't have time to look too deep
into it, but I figure that I would report it.

-- Steve

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