Messages in this thread |  | | | Date | Sun, 20 Mar 2005 17:57:23 +0100 | | From | Manfred Spraul <> | | Subject | Re: Real-Time Preemption and RCU |
Thomas Gleixner wrote:
>On Sun, 2005-03-20 at 07:36 +0100, Manfred Spraul wrote: > > >>cpu 1: >>acquire random networking spin_lock_bh() >> >>cpu 2: >>read_lock(&tasklist_lock) from process context >>interrupt. softirq. within softirq: try to acquire the networking lock. >>* spins. >> >>cpu 1: >>hardware interrupt >>within hw interrupt: signal delivery. tries to acquire tasklist_lock. >> >>--> deadlock. >> >> > >Signal delivery from hw interrupt context (interrupt is flagged >SA_NODELAY) is not possible in RT preemption mode. The >local_irq_save_nort() check in __cache_alloc will catch you. > > > That was just one random example. Another one would be :
drivers/chat/tty_io.c, __do_SAK() contains read_lock(&tasklist_lock); task_lock(p);
kernel/sys.c, sys_setrlimit contains task_lock(current->group_leader); read_lock(&tasklist_lock);
task_lock is a shorthand for spin_lock(&p->alloc_lock). If read_lock is a normal spinlock, then this is an A/B B/A deadlock.
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