Messages in this thread Patch in this message | | | From | Charan Teja Reddy <> | Subject | [PATCH V2] sched,psi: fix the 'int' underflow for psi | Date | Fri, 16 Apr 2021 20:32:16 +0530 |
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psi_group_cpu->tasks, represented by the unsigned int, stores the number of tasks that could be stalled on a psi resource(io/mem/cpu). Decrementing these counters at zero leads to wrapping which further leads to the psi_group_cpu->state_mask is being set with the respective pressure state. This could result into the unnecessary time sampling for the pressure state thus cause the spurious psi events. This can further lead to wrong actions being taken at the user land based on these psi events. Though psi_bug is set under these conditions but that just for debug purpose. Fix it by decrementing the ->tasks count only when it is non-zero.
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org> --- Changes in V1: https://lore.kernel.org/patchwork/patch/1413894/
kernel/sched/psi.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 967732c..651218d 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -711,14 +711,15 @@ static void psi_group_change(struct psi_group *group, int cpu, for (t = 0, m = clear; m; m &= ~(1 << t), t++) { if (!(m & (1 << t))) continue; - if (groupc->tasks[t] == 0 && !psi_bug) { + if (groupc->tasks[t]) { + groupc->tasks[t]--; + } else if (!psi_bug) { printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u] clear=%x set=%x\n", cpu, t, groupc->tasks[0], groupc->tasks[1], groupc->tasks[2], groupc->tasks[3], clear, set); psi_bug = 1; } - groupc->tasks[t]--; } for (t = 0; set; set &= ~(1 << t), t++) -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation
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