This completes the xchg implementation for sh architecture. Note: The
llsc variant is tricky since this only supports 4 byte atomics, the
existing implementation of 1 byte xchg is wrong: we need to do a 4 byte
cmpxchg and retry if any bytes changed meanwhile.
Write this in C for clarity.
Suggested-by: Rich Felker <dalias@libc.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
gUSA special cases r15 for part of its login/out sequence, meaning that
any parameters need to be explicitly prohibited from accidentally being
assigned that particular register, and the compiler ultimately needs to
use a temporary instead.
Certain configurations have begun generating code paths that do indeed
get allocated r15, resulting in immediate corruption of the exchanged
value. This was observed in (amongst others) exit_mm() code generation
where the xchg_u32 call was immediately corrupting a structure address.
As this is a general gUSA restriction, the rest of the users likewise
need to be updated to ensure sensible constraints.
References: https://bugzilla.stlinux.com/show_bug.cgi?id=11229
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Reviewed-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This patch fixes a bug within the cmpxchg GRB version.
A problem was notices while running some tests to stress
the priority inheritance, for example pi_stress
(http://rt.wiki.kernel.org/index.php/PI_Mutex_Test).
Also, without this patch, after applying the latest work to
consolidate atomic_cmpxchg() definitions (commit:
8c0b8139c8)
the Kernel doesn't boot at all.
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This follows the sparc changes a439fe51a1.
Most of the moving about was done with Sam's directions at:
http://marc.info/?l=linux-sh&m=121724823706062&w=2
with subsequent hacking and fixups entirely my fault.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Michael S. Tsirkin