Hi, I'm sending an email to discuss how to remove spinlock from a whole process of open/read/close of efi_pstore.
[Problem] Current efi_pstore calls kmalloc() in a read callback while holding a spinlock, efivar->lock, in an open callback. This means efi_pstore may deadlock if it sleeps in kmalloc(). Also, there is a comment that an efivar->lock shouldn't be held when calling kmalloc(). [Idea] In a process of open/read/close, pstore creates some files in the directory of /dev/pstore. So, memory allocations like kmalloc() are not avoidable. My idea fixing this issue is removing spinlock from a whole process of open/read/close of efi_pstore. Currently, efivar->lock protects two things, efivar->list and ops.[gs]et_variable(). But if we can revise locks of efivar as follows, we can fix this issue. - Introduce a new efivar->list_lock to protect efivar->list and RCU is used while searching it. - An existing efivar>lock protects just ops.[gs]et_variable() calls. Any comments are welcome. Seiji -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
