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Date: Thu, 10 Nov 2022 14:53:44 +0100 From: Peter Newman <peternewman@...gle.com> To: reinette.chatre@...el.com, fenghua.yu@...el.com Cc: bp@...en8.de, derkling@...gle.com, eranian@...gle.com, hpa@...or.com, james.morse@....com, jannh@...gle.com, kpsingh@...gle.com, linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de, x86@...nel.org, Peter Newman <peternewman@...gle.com> Subject: [PATCH v2 0/1] x86/resctrl: fix task CLOSID update race Hi Reinette, Fenghua, Below is my updated patch to address the IPI race we discussed in the container move RFD thread[1]. The patch below uses the new task_call_func() interface to serialize updating closid and rmid with any context switch of the task. AFAICT, the implementation of this function acts like a mutex with context switch, but I'm not certain whether it is intended to be one. If this is not how task_call_func() is meant to be used, I will instead move the code performing the update under sched/ where it can be done holding the task_rq_lock() explicitly, as Reinette has suggested before[2]. task_call_func() is only used when moving as single task, as group changes would require task_call_func() to be called on every task in a potentially large list, which is likely more detrimental than an IPI broadcast. Furthermore, when moving a large group, the resulting CPU update mask will probably contain all CPUs anyways. Updates since v1: - 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/ Thanks! -Peter [1] https://lore.kernel.org/all/CALPaoCg2-9ARbK+MEgdvdcjJtSy_2H6YeRkLrT97zgy8Aro3Vg@mail.gmail.com/ [2] https://lore.kernel.org/lkml/d3c06fa3-83a4-7ade-6b08-3a7259aa6c4b@intel.com/ Peter Newman (1): x86/resctrl: fix task closid/rmid update race arch/x86/kernel/cpu/resctrl/rdtgroup.c | 134 ++++++++++++------------- 1 file changed, 62 insertions(+), 72 deletions(-) -- 2.38.1.431.g37b22c650d-goog
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