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scx: Fix local DSQ comparison in dispatch_to_local_dsq() #219
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@Gabant noticed in #218 that our comparison is backwards in dispatch_to_local_dsq() when determining if the destination rq in a local dispatch is idle. This could cause us to fail to send resched IPIs to those remote DSQs when a scheduler uses SCX_DSQ_LOCAL_ON when dispatching. Thankfully, the issue doesn't happen if dispatching to a local DSQ from the ops.select_cpu() path, as a resched IPI is sent by the core scheduler if a task is migrated to an idle core on the wakeup path. Let's fix it. Reported-by: @Gabant Signed-off-by: David Vernet <[email protected]>
We should have _some_ test that exercises that codepath. Signed-off-by: David Vernet <[email protected]>
htejun
approved these changes
Jun 5, 2024
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@Gabant noticed in #218 that our
comparison is backwards in dispatch_to_local_dsq() when determining if the
destination rq in a local dispatch is idle. This could cause us to fail to send
resched IPIs to those remote DSQs when a scheduler uses SCX_DSQ_LOCAL_ON when
dispatching. Thankfully, the issue doesn't happen if dispatching to a local DSQ
from the ops.select_cpu() path, as a resched IPI is sent by the core scheduler
if a task is migrated to an idle core on the wakeup path.
Let's fix it.
Reported-by: @Gabant
Signed-off-by: David Vernet [email protected]