For kernels built with CONFIG_FORCE_NR_CPUS=y, the nr_cpu_ids is defined as NR_CPUS instead of the number of possible cpus, this will cause the following system panic:
[ 0.015349][ T0] smpboot: Allowing 4 CPUs, 0 hotplug CPUs ... [ 0.021342][ T0] setup_percpu: NR_CPUS:512 nr_cpumask_bits:512 nr_cpu_ids:512 nr_node_ids:1 ... [ 3.681252][ T15] BUG: unable to handle page fault for address: ffffffff9911c8c8 [ 3.689415][ T45] ehci-pci 0000:00:1a.0: debug port 2 [ 3.697008][ T15] #PF: supervisor read access in kernel mode [ 3.697009][ T15] #PF: error_code(0x0000) - not-present page [ 3.706233][ T45] ehci-pci 0000:00:1a.0: irq 16, io mem 0xf7e3c000 [ 3.708152][ T15] PGD 40fa24067 P4D 40fa24067 PUD 40fa25063 PMD 410bff063 [ 3.720380][ T45] ehci-pci 0000:00:1a.0: USB 2.0 started, EHCI 1.00 [ 3.720430][ T15] PTE 800ffffbefee3062 [ 3.720431][ T15] Oops: 0000 [#1] PREEMPT SMP PTI [ 3.727873][ T45] usb usb2: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 6.06 [ 3.734009][ T15] CPU: 0 PID: 15 Comm: rcu_tasks_trace Tainted: G W 6.6.21 #1 5dc7acf91a5e8e9ac9dcfc35bee0245691283ea6 [ 3.734011][ T15] Hardware name: Dell Inc. OptiPlex 9020/005T15, BIOS A14 09/14/2015 [ 3.734012][ T15] RIP: 0010:rcu_tasks_need_gpcb+0x25d/0x2c0 [ 3.737962][ T45] usb usb2: New USB device strings: Mfr=3, Product=2, SerialNumber=1 [ 3.742877][ T15] RSP: 0018:ffffa371c00a3e60 EFLAGS: 00010082 [ 3.751891][ T45] usb usb2: Product: EHCI Host Controller [ 3.764495][ T15] [ 3.764496][ T15] RAX: ffffffff98929ca0 RBX: ffffffff98b3b328 RCX: 0000000000021880 [ 3.764497][ T15] RDX: ffffffff9911c880 RSI: 0000000000000000 RDI: 0000000000000000 [ 3.772461][ T45] usb usb2: Manufacturer: Linux 6.6.21 ehci_hcd [ 3.778248][ T15] RBP: 0000000000000202 R08: 0000000000000000 R09: 0000000000000000 [ 3.778249][ T15] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000003 [ 3.778249][ T15] R13: 0000000000000000 R14: 0000000000000001 R15: ffffffff98b3b320 [ 3.786216][ T45] usb usb2: SerialNumber: 0000:00:1a.0 [ 3.805811][ T15] FS: 0000000000000000(0000) GS:ffff8c781ea00000(0000) knlGS:0000000000000000 [ 3.805813][ T15] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3.811993][ T45] hub 2-0:1.0: USB hub found [ 3.817383][ T15] CR2: ffffffff9911c8c8 CR3: 000000040fa20005 CR4: 00000000001706f0 [ 3.817385][ T15] Call Trace: [ 3.817386][ T15] <TASK> [ 3.817388][ T15] ? __die+0x23/0x80 [ 3.819643][ T45] hub 2-0:1.0: 2 ports detected [ 3.827481][ T15] ? page_fault_oops+0xa4/0x180 [ 3.827485][ T15] ? exc_page_fault+0x152/0x180 [ 3.922376][ T15] ? asm_exc_page_fault+0x26/0x40 [ 3.927289][ T15] ? rcu_tasks_need_gpcb+0x25d/0x2c0 [ 3.932459][ T15] ? __pfx_rcu_tasks_kthread+0x40/0x40 [ 3.937806][ T15] rcu_tasks_one_gp+0x69/0x180 [ 3.942451][ T15] rcu_tasks_kthread+0x94/0xc0 [ 3.947096][ T15] kthread+0xe8/0x140 [ 3.950956][ T15] ? __pfx_kthread+0x40/0x40 [ 3.955425][ T15] ret_from_fork+0x34/0x80 [ 3.959721][ T15] ? __pfx_kthread+0x40/0x40 [ 3.964192][ T15] ret_from_fork_asm+0x1b/0x80 [ 3.968841][ T15] </TASK> Consider that there may be holes in the CPU numbers, this commit use the maxcpu variable to store the CPU numbers after traversing possible cpu, and generate the rcu_task_cpu_ids variable and assign it to (maxcpu +1) instead of nr_cpu_ids. Closes: https://lore.kernel.org/linux-input/calma0xatsmn+p4xuxkzrtr5r6k7hgoswcaxx7bar_z9r5jj...@mail.gmail.com/T/#u Reported-by: Zhixu Liu <[email protected]> Signed-off-by: Zqiang <[email protected]> --- kernel/rcu/tasks.h | 78 +++++++++++++++++++++++++++++----------------- 1 file changed, 49 insertions(+), 29 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index e362f72bb65d..22310965acc7 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -49,6 +49,7 @@ struct rcu_tasks_percpu { struct list_head rtp_blkd_tasks; struct list_head rtp_exit_list; int cpu; + int index; struct rcu_tasks *rtpp; }; @@ -110,6 +111,7 @@ struct rcu_tasks { call_rcu_func_t call_func; unsigned int wait_state; struct rcu_tasks_percpu __percpu *rtpcpu; + struct rcu_tasks_percpu **rtpcp_array; int percpu_enqueue_shift; int percpu_enqueue_lim; int percpu_dequeue_lim; @@ -182,6 +184,8 @@ module_param(rcu_task_collapse_lim, int, 0444); static int rcu_task_lazy_lim __read_mostly = 32; module_param(rcu_task_lazy_lim, int, 0444); +static int rcu_task_cpu_ids; + /* RCU tasks grace-period state for debugging. */ #define RTGS_INIT 0 #define RTGS_WAIT_WAIT_CBS 1 @@ -245,6 +249,8 @@ static void cblist_init_generic(struct rcu_tasks *rtp) int cpu; int lim; int shift; + int maxcpu; + int index = 0; if (rcu_task_enqueue_lim < 0) { rcu_task_enqueue_lim = 1; @@ -254,14 +260,9 @@ static void cblist_init_generic(struct rcu_tasks *rtp) } lim = rcu_task_enqueue_lim; - if (lim > nr_cpu_ids) - lim = nr_cpu_ids; - shift = ilog2(nr_cpu_ids / lim); - if (((nr_cpu_ids - 1) >> shift) >= lim) - shift++; - WRITE_ONCE(rtp->percpu_enqueue_shift, shift); - WRITE_ONCE(rtp->percpu_dequeue_lim, lim); - smp_store_release(&rtp->percpu_enqueue_lim, lim); + rtp->rtpcp_array = kcalloc(num_possible_cpus(), sizeof(struct rcu_tasks_percpu *), GFP_KERNEL); + BUG_ON(!rtp->rtpcp_array); + for_each_possible_cpu(cpu) { struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu); @@ -273,14 +274,29 @@ static void cblist_init_generic(struct rcu_tasks *rtp) INIT_WORK(&rtpcp->rtp_work, rcu_tasks_invoke_cbs_wq); rtpcp->cpu = cpu; rtpcp->rtpp = rtp; + rtpcp->index = index; + rtp->rtpcp_array[index] = rtpcp; + index++; if (!rtpcp->rtp_blkd_tasks.next) INIT_LIST_HEAD(&rtpcp->rtp_blkd_tasks); if (!rtpcp->rtp_exit_list.next) INIT_LIST_HEAD(&rtpcp->rtp_exit_list); + maxcpu = cpu; } - pr_info("%s: Setting shift to %d and lim to %d rcu_task_cb_adjust=%d.\n", rtp->name, - data_race(rtp->percpu_enqueue_shift), data_race(rtp->percpu_enqueue_lim), rcu_task_cb_adjust); + rcu_task_cpu_ids = maxcpu + 1; + if (lim > rcu_task_cpu_ids) + lim = rcu_task_cpu_ids; + shift = ilog2(rcu_task_cpu_ids / lim); + if (((rcu_task_cpu_ids - 1) >> shift) >= lim) + shift++; + WRITE_ONCE(rtp->percpu_enqueue_shift, shift); + WRITE_ONCE(rtp->percpu_dequeue_lim, lim); + smp_store_release(&rtp->percpu_enqueue_lim, lim); + + pr_info("%s: Setting shift to %d and lim to %d rcu_task_cb_adjust=%d rcu_task_cpu_ids=%d.\n", + rtp->name, data_race(rtp->percpu_enqueue_shift), data_race(rtp->percpu_enqueue_lim), + rcu_task_cb_adjust, rcu_task_cpu_ids); } // Compute wakeup time for lazy callback timer. @@ -348,7 +364,7 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func, rtpcp->rtp_n_lock_retries = 0; } if (rcu_task_cb_adjust && ++rtpcp->rtp_n_lock_retries > rcu_task_contend_lim && - READ_ONCE(rtp->percpu_enqueue_lim) != nr_cpu_ids) + READ_ONCE(rtp->percpu_enqueue_lim) != rcu_task_cpu_ids) needadjust = true; // Defer adjustment to avoid deadlock. } // Queuing callbacks before initialization not yet supported. @@ -368,10 +384,10 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func, raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags); if (unlikely(needadjust)) { raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags); - if (rtp->percpu_enqueue_lim != nr_cpu_ids) { + if (rtp->percpu_enqueue_lim != rcu_task_cpu_ids) { WRITE_ONCE(rtp->percpu_enqueue_shift, 0); - WRITE_ONCE(rtp->percpu_dequeue_lim, nr_cpu_ids); - smp_store_release(&rtp->percpu_enqueue_lim, nr_cpu_ids); + WRITE_ONCE(rtp->percpu_dequeue_lim, rcu_task_cpu_ids); + smp_store_release(&rtp->percpu_enqueue_lim, rcu_task_cpu_ids); pr_info("Switching %s to per-CPU callback queuing.\n", rtp->name); } raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags); @@ -481,7 +497,7 @@ static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp) if (rcu_task_cb_adjust && ncbs <= rcu_task_collapse_lim) { raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags); if (rtp->percpu_enqueue_lim > 1) { - WRITE_ONCE(rtp->percpu_enqueue_shift, order_base_2(nr_cpu_ids)); + WRITE_ONCE(rtp->percpu_enqueue_shift, order_base_2(rcu_task_cpu_ids)); smp_store_release(&rtp->percpu_enqueue_lim, 1); rtp->percpu_dequeue_gpseq = get_state_synchronize_rcu(); gpdone = false; @@ -496,7 +512,9 @@ static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp) pr_info("Completing switch %s to CPU-0 callback queuing.\n", rtp->name); } if (rtp->percpu_dequeue_lim == 1) { - for (cpu = rtp->percpu_dequeue_lim; cpu < nr_cpu_ids; cpu++) { + for (cpu = rtp->percpu_dequeue_lim; cpu < rcu_task_cpu_ids; cpu++) { + if (!cpu_possible(cpu)) + continue; struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu); WARN_ON_ONCE(rcu_segcblist_n_cbs(&rtpcp->cblist)); @@ -511,30 +529,32 @@ static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp) // Advance callbacks and invoke any that are ready. static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu *rtpcp) { - int cpu; - int cpunext; int cpuwq; unsigned long flags; int len; + int index; struct rcu_head *rhp; struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl); struct rcu_tasks_percpu *rtpcp_next; - cpu = rtpcp->cpu; - cpunext = cpu * 2 + 1; - if (cpunext < smp_load_acquire(&rtp->percpu_dequeue_lim)) { - rtpcp_next = per_cpu_ptr(rtp->rtpcpu, cpunext); - cpuwq = rcu_cpu_beenfullyonline(cpunext) ? cpunext : WORK_CPU_UNBOUND; - queue_work_on(cpuwq, system_wq, &rtpcp_next->rtp_work); - cpunext++; - if (cpunext < smp_load_acquire(&rtp->percpu_dequeue_lim)) { - rtpcp_next = per_cpu_ptr(rtp->rtpcpu, cpunext); - cpuwq = rcu_cpu_beenfullyonline(cpunext) ? cpunext : WORK_CPU_UNBOUND; + index = rtpcp->index * 2 + 1; + if (index < num_possible_cpus()) { + rtpcp_next = rtp->rtpcp_array[index]; + if (rtpcp_next->cpu < smp_load_acquire(&rtp->percpu_dequeue_lim)) { + cpuwq = rcu_cpu_beenfullyonline(rtpcp_next->cpu) ? rtpcp_next->cpu : WORK_CPU_UNBOUND; queue_work_on(cpuwq, system_wq, &rtpcp_next->rtp_work); + index++; + if (index < num_possible_cpus()) { + rtpcp_next = rtp->rtpcp_array[index]; + if (rtpcp_next->cpu < smp_load_acquire(&rtp->percpu_dequeue_lim)) { + cpuwq = rcu_cpu_beenfullyonline(rtpcp_next->cpu) ? rtpcp_next->cpu : WORK_CPU_UNBOUND; + queue_work_on(cpuwq, system_wq, &rtpcp_next->rtp_work); + } + } } } - if (rcu_segcblist_empty(&rtpcp->cblist) || !cpu_possible(cpu)) + if (rcu_segcblist_empty(&rtpcp->cblist)) return; raw_spin_lock_irqsave_rcu_node(rtpcp, flags); rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq)); -- 2.17.1
