[Bug nptl/15640] The ARM port of lll_unlock uses atomic compare and swap to release a lock

["dtemirbulatov at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=15640

Dinar Temirbulatov <dtemirbulatov at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |dtemirbulatov at gmail dot com
         Resolution|---                         |INVALID

--- Comment #1 from Dinar Temirbulatov <dtemirbulatov at gmail dot com> ---
This report looks invalid to me. The lll_unlock could not be done without
proper atomic operation atomic_exchange_rel. Here is the use-case:

thread A has the lock and wants to release it with lll_unlock
thread B is about to acquire the lock
thread A does READ, sets oldval to "1"
thread B call lll_lock, sets *__futex to 2 and goes to sleep.
thread A does DMB, sets *__futex to "0"
thread A does NOT call lll_futex_wake because oldval is "1"
thread B sleeps forever.
bug

Resolving bug as INVALID.

-- 
You are receiving this mail because:
You are on the CC list for the bug.