Messages in this thread |  | | Subject | logbuf_lock deadlock on NMI | From | Luca Barbieri <> | Date | 31 Aug 2002 11:12:19 +0200 |
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I already mentioned this in an unrelated thread but I got no responses.
NMIs, by definition and documentation, are non maskable. This means that we can get them anywhere, even when interrupts are disabled.
The problem is that in some paths of the NMI handler (mem_parity_error, io_check_error, mca_handle_nmi), we call printk without busting spinlocks first. As a consequence, if I'm not missing something, if we get e.g. a memory parity error while inside printk, we deadlock on logbuf_lock.
Apart from removing logbuf_lock and other locks that might be held in printk, we could solve this by telling the APIC (I think that the same can be done with the 8259 but I'm not sure) to send an interrupt to the current CPU. The interrupt, being maskable, will be triggered only outside irq-protected spinlocks so we can safely do the NMI printk inside it.
Alternatively we may just reset the locks but since some errors are non-fatal it probably isn't a good idea.
Any comments?
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