From f6b6a28e2dbc401416ff12f775d75281c9b41918 Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Fri, 29 Jul 2016 16:15:18 -0300 Subject: [PATCH] nvme: Prevent controller state invalid transition Acquiring the nvme_ctrl lock before reading ctrl->state in nvme_change_ctrl_state() should prevent a theoretical invalid state transition, in the event of two threads racing inside that function. I haven't been able to observe this happening with the current code, and the current state machine seems to be simple enough to not be affected by these invalid transitions, but future modifications could make it more likely to happen. Signed-off-by: Gabriel Krisman Bertazi Reviewed-by: Sagi Grimberg Reviewed-by: Steve Wise Signed-off-by: Jens Axboe --- drivers/nvme/host/core.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 7ff2e820bbf4..7f75d661237f 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -81,10 +81,12 @@ EXPORT_SYMBOL_GPL(nvme_cancel_request); bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl, enum nvme_ctrl_state new_state) { - enum nvme_ctrl_state old_state = ctrl->state; + enum nvme_ctrl_state old_state; bool changed = false; spin_lock_irq(&ctrl->lock); + + old_state = ctrl->state; switch (new_state) { case NVME_CTRL_LIVE: switch (old_state) { @@ -140,11 +142,12 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl, default: break; } - spin_unlock_irq(&ctrl->lock); if (changed) ctrl->state = new_state; + spin_unlock_irq(&ctrl->lock); + return changed; } EXPORT_SYMBOL_GPL(nvme_change_ctrl_state); -- 2.20.1