Thadeu Lima de Souza Cascardo
authored
When reading blkio.throttle.io_serviced in a recently created blkio cgroup, it's possible to race against the creation of a throttle policy, which delays the allocation of stats_cpu. Like other functions in the throttle code, just checking for a NULL stats_cpu prevents the following oops caused by that race. [ 1117.285199] Unable to handle kernel paging request for data at address 0x7fb4d0020 [ 1117.285252] Faulting instruction address: 0xc0000000003efa2c [ 1137.733921] Oops: Kernel access of bad area, sig: 11 [#1] [ 1137.733945] SMP NR_CPUS=2048 NUMA PowerNV [ 1137.734025] Modules linked in: bridge stp llc kvm_hv kvm binfmt_misc autofs4 [ 1137.734102] CPU: 3 PID: 5302 Comm: blkcgroup Not tainted 3.19.0 #5 [ 1137.734132] task: c000000f1d188b00 ti: c000000f1d210000 task.ti: c000000f1d210000 [ 1137.734167] NIP: c0000000003efa2c LR: c0000000003ef9f0 CTR: c0000000003ef980 [ 1137.734202] REGS: c000000f1d213500 TRAP: 0300 Not tainted (3.19.0) [ 113...