diff options
| author | Palmer Dabbelt | 2020-07-16 11:57:26 -0700 |
|---|---|---|
| committer | Palmer Dabbelt | 2020-07-17 09:28:35 -0700 |
| commit | 38b7c2a3ffb1fce8358ddc6006cfe5c038ff9963 (patch) | |
| tree | 95be1d51d69478dbf93f5bb8c2a4e6c7729d21f9 | |
| parent | 0cac21b02ba5f3095fd2dcc77c26a25a0b2432ed (diff) | |
RISC-V: Upgrade smp_mb__after_spinlock() to iorw,iorw
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>
| -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> |