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In task_init() there is a calculation of machdep->hz based on the value of cfq_slice_async if the symbol exists: if (symbol_exists("cfq_slice_async")) { uint cfq_slice_async; get_symbol_data("cfq_slice_async", sizeof(int), &cfq_slice_async); if (cfq_slice_async) { machdep->hz = cfq_slice_async * 25; if (CRASHDEBUG(2)) fprintf(fp, "cfq_slice_async exists: setting hz to %d\n", machdep->hz); } } However, patch “cfq-iosched: Convert from jiffies to nanoseconds” (https://patchwork.kernel.org/project/linux-block/patch/1465391499-27867-2-git-send-email-jack@xxxxxxx/)
changed the definition of cfq_slice_async from (HZ / 25) to (NSEC_PER_SEC / 25). As such, the above calculation will result in a value of 1000000000 for machdep->hz. In vmcores where the symbol exists and has this definition, this causes incorrect results
for some calculations. I have a couple of 4.12 vmcores in this situation, and in them crash shows the uptime as 3 seconds, which also throws off the timestamps in “log -T”. Fix this by skipping the above code block for kernels 4.8 and above: --- task.c.orig 2021-04-14 16:07:52.021137849 -0400 +++ task.c 2021-04-14 16:11:03.406626370 -0400 @@ -417,7 +417,8 @@ STRUCT_SIZE_INIT(cputime_t, "cputime_t"); - if (symbol_exists("cfq_slice_async")) { + if ((THIS_KERNEL_VERSION < LINUX(4,8,0)) && + symbol_exists("cfq_slice_async")) { uint cfq_slice_async; get_symbol_data("cfq_slice_async", sizeof(int), Martin Moore HPE Pointnext Services |
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