[PATCH v6 04/15] memory-hotplug: remove /sys/firmware/memmap/X sysfs
tangchen at cn.fujitsu.com
Thu Jan 10 17:15:04 EST 2013
On 01/10/2013 07:19 AM, Andrew Morton wrote:
>> + entry = firmware_map_find_entry(start, end - 1, type);
>> + if (!entry)
>> + return -EINVAL;
>> + firmware_map_remove_entry(entry);
> The above code looks racy. After firmware_map_find_entry() does the
> spin_unlock() there is nothing to prevent a concurrent
> firmware_map_remove_entry() from removing the entry, so the kernel ends
> up calling firmware_map_remove_entry() twice against the same entry.
> An easy fix for this is to hold the spinlock across the entire
> lookup/remove operation.
> This problem is inherent to firmware_map_find_entry() as you have
> implemented it, so this function simply should not exist in the current
> form - no caller can use it without being buggy! A simple fix for this
> is to remove the spin_lock()/spin_unlock() from
> firmware_map_find_entry() and add locking documentation to
> firmware_map_find_entry(), explaining that the caller must hold
> map_entries_lock and must not release that lock until processing of
> firmware_map_find_entry()'s return value has completed.
Thank you for your advice, I'll fix it soon.
Since you have merged the patch-set, do I need to resend all these
patches again, or just send a patch to fix it based on the current
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