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Subject[PATCH v5 0/1] Subject: x86/resctrl: Fix task CLOSID update race
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Hi Reinette, Fenghua,

Now that we know there is a full barrier in context switch and that
smp_mb() on every task in a group update isn't nearly as expensive as
task_call_func(), I can present you a much smaller fix.

The diffs are small enough to go down to a single patch. The changelogs
are not much simpler, but hopefully this isn't as big of a concern.

This patch is different enough that I thought it necessary to remove
James's Reviewed-By.

Updates in v5:
- Just put an smp_mb() between CLOSID/RMID stores and task_curr() calls
- Add a diagram detailing the race to the changelog
Updates in v4:
- Reorder the patches so that justification for sending more IPIs can
reference the patch fixing __rdtgroup_move_task().
- Correct tense of wording used in changelog and comments
Updates in v3:
- Split the handling of multi-task and single-task operations into
separate patches, now that they're handled differently.
- Clarify justification in the commit message, including moving some of
it out of inline code comment.
Updates in v2:
- Following Reinette's suggestion: use task_call_func() for single
task, IPI broadcast for group movements.
- Rebased to v6.1-rc4

v1: https://lore.kernel.org/lkml/20221103141641.3055981-1-peternewman@google.com/
v2: https://lore.kernel.org/lkml/20221110135346.2209839-1-peternewman@google.com/
v3: https://lore.kernel.org/lkml/20221115141953.816851-1-peternewman@google.com/
v4: https://lore.kernel.org/lkml/20221129111055.953833-1-peternewman@google.com/

Thank you for your careful reviews and feedback so far.

-Peter

Peter Newman (1):
x86/resctrl: Fix task CLOSID/RMID update race

arch/x86/kernel/cpu/resctrl/rdtgroup.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)


base-commit: 830b3c68c1fb1e9176028d02ef86f3cf76aa2476
--
2.39.0.rc1.256.g54fd8350bd-goog

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