diff options
author | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-07-16 11:57:26 -0700 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-07-29 10:18:40 +0200 |
commit | 35728cac176a1cc1c57aa87a1e55e95a0ee3e985 (patch) | |
tree | 3188c3cd195c8715955b2423525127f43ce8a3b9 /arch/riscv | |
parent | 5345ede4acde4dc6ea54841917a8c671e39599da (diff) |
RISC-V: Upgrade smp_mb__after_spinlock() to iorw,iorw
[ Upstream commit 38b7c2a3ffb1fce8358ddc6006cfe5c038ff9963 ]
While digging through the recent mmiowb preemption issue it came up that
we aren't actually preventing IO from crossing a scheduling boundary.
While it's a bit ugly to overload smp_mb__after_spinlock() with this
behavior, it's what PowerPC is doing so there's some precedent.
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'arch/riscv')
-rw-r--r-- | arch/riscv/include/asm/barrier.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/riscv/include/asm/barrier.h b/arch/riscv/include/asm/barrier.h index 3f1737f301cc..d0e24aaa2aa0 100644 --- a/arch/riscv/include/asm/barrier.h +++ b/arch/riscv/include/asm/barrier.h @@ -58,8 +58,16 @@ do { \ * The AQ/RL pair provides a RCpc critical section, but there's not really any * way we can take advantage of that here because the ordering is only enforced * on that one lock. Thus, we're just doing a full fence. + * + * Since we allow writeX to be called from preemptive regions we need at least + * an "o" in the predecessor set to ensure device writes are visible before the + * task is marked as available for scheduling on a new hart. While I don't see + * any concrete reason we need a full IO fence, it seems safer to just upgrade + * this in order to avoid any IO crossing a scheduling boundary. In both + * instances the scheduler pairs this with an mb(), so nothing is necessary on + * the new hart. */ -#define smp_mb__after_spinlock() RISCV_FENCE(rw,rw) +#define smp_mb__after_spinlock() RISCV_FENCE(iorw,iorw) #include <asm-generic/barrier.h> |