Looking at mainline's down_read() I noticed that reader locks of rwsems
are not made to nest. In fact, they should not. Although, it may seem
fine if a down_read() nests as multiple readers can have the lock,
rwsems are fair locks. That is, if a writer were to block on a rwsem
while readers have the lock, a new reader will also block. If a reader
were to try to take the lock again while a writer was waiting, it
would block, and cause a deadlock as it has the lock its trying
to grab and wont let it go as the writer is waiting.
I also found that the rt_mutex_init() is identical in the two places
it is defined in rtmutex.h.
Steven Rostedt (Red Hat) (2):
rwsem-rt: Do not allow readers to nest
rtmutex: Remove duplicate rt_mutex_init()
----
include/linux/rtmutex.h | 12 +++---------
include/linux/rwsem_rt.h | 1 -
kernel/rt.c | 37 ++++++++-----------------------------
3 files changed, 11 insertions(+), 39 deletions(-)
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