Messages in this thread | | | Date | Thu, 10 Jan 2013 14:15:04 +0800 | From | Tang Chen <> | Subject | Re: [PATCH v6 04/15] memory-hotplug: remove /sys/firmware/memmap/X sysfs |
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Hi Andrew,
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 one ?
Thanks. :)
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