[PATCH v2] rcu-tasks: Fix access non-existent percpu rtpcp variable in rcu_tasks_need_gpcb()
From: Zqiang
Date: Tue Jun 04 2024 - 04:55:16 EST
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_z9r5jjskw@xxxxxxxxxxxxxx/T/#u
Reported-by: Zhixu Liu <zhixu.liu@xxxxxxxxx>
Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx>
---
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