iwlwifi: pcie: reschedule in long-running memory reads
[ Upstream commit 3d372c4e ] If we spin for a long time in memory reads that (for some reason in hardware) take a long time, then we'll eventually get messages such as watchdog: BUG: soft lockup - CPU#2 stuck for 24s! [kworker/2:2:272] This is because the reading really does take a very long time, and we don't schedule, so we're hogging the CPU with this task, at least if CONFIG_PREEMPT is not set, e.g. with CONFIG_PREEMPT_VOLUNTARY=y. Previously I misinterpreted the situation and thought that this was only going to happen if we had interrupts disabled, and then fixed this (which is good anyway, however), but that didn't always help; looking at it again now I realized that the spin unlock will only reschedule if CONFIG_PREEMPT is used. In order to avoid this issue, change the code to cond_resched() if we've been spinning for too long here. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Fixes: 04516706 ("iwlwifi: pcie: limit memory read spin time") Signed-off-by: Luca Coelho <luciano.coelho@intel.com> Signed-off-by: Kalle Valo <kvalo@codeaurora.org> Link: https://lore.kernel.org/r/iwlwifi.20210115130253.217a9d6a6a12.If964cb582ab0aaa94e81c4ff3b279eaafda0fd3f@changeid Signed-off-by: Sasha Levin <sashal@kernel.org>
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