[LU-8492] ptlrpc: Correctly calculate hrp->hrp_nthrs

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.9.0
• Severity: 3
• Assignee: Amir Shehata (Inactive)
• Reporter: Joseph Gmitter (Inactive)

Description

This ticket separates out patch http://review.whamcloud.com/#/c/19106/ from LU-6285 was already resolved when the new issue was identified (as noted in LU-6285)

It addresses the following:

There is still an issue which could cause the assert.

cpu_pattern can sepcify exactly 1 cpu in a partition:
"0[0]". That means CPT0 will have CPU 0. CPU 0 can have
hyperthreading enabled. This combination would result in

weight = cfs_cpu_ht_nsiblings(0);
hrp->hrp_nthrs = cfs_cpt_weight(ptlrpc_hr.hr_cpt_table, i);
hrp->hrp_nthrs /= weight;

evaluating to 0. Where

cfs_cpt_weight(ptlrpc_hr.hr_cpt_table, i) == 1
weight == 2

Therefore only divide out with weight if

hrp->hrp_nthrs >= weight

This will avoid the assert:

LASSERT(hrp->hrp_nthrs > 0);

Issue Links

• is related to: LU-8451 assert if cpu_pattern specifies exactly one cpu in the partition
• is related to: LU-6285 Assert fails in staging client module crashes kernel if CPUMASK_OFFSTACK set