linux-stable.git/kernel/rcu, branch linux-6.11.y Linux kernel stable tree rcuscale: Do a proper cleanup if kfree_scale_init() fails 2024-12-05T12:52:53+00:00 Uladzislau Rezki (Sony) urezki@gmail.com 2024-11-13T11:00:08+00:00 e1a056235f3fa283db779279d75053ebb07a6ef3 [ Upstream commit 812a1c3b9f7c36d9255f0d29d0a3d324e2f52321 ] A static analyzer for C, Smatch, reports and triggers below warnings: kernel/rcu/rcuscale.c:1215 rcu_scale_init() warn: inconsistent returns 'global &fullstop_mutex'. The checker complains about, we do not unlock the "fullstop_mutex" mutex, in case of hitting below error path: <snip> ... if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) { pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n"); WARN_ON_ONCE(1); return -1; ^^^^^^^^^^ ... <snip> it happens because "-1" is returned right away instead of doing a proper unwinding. Fix it by jumping to "unwind" label instead of returning -1. Reported-by: Dan Carpenter <dan.carpenter@linaro.org> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Closes: https://lore.kernel.org/rcu/ZxfTrHuEGtgnOYWp@pc636/T/ Fixes: 084e04fff160 ("rcuscale: Add laziness and kfree tests") Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 812a1c3b9f7c36d9255f0d29d0a3d324e2f52321 ]

A static analyzer for C, Smatch, reports and triggers below
warnings:

   kernel/rcu/rcuscale.c:1215 rcu_scale_init()
   warn: inconsistent returns 'global &fullstop_mutex'.

The checker complains about, we do not unlock the "fullstop_mutex"
mutex, in case of hitting below error path:

<snip>
...
    if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) {
        pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n");
        WARN_ON_ONCE(1);
        return -1;
        ^^^^^^^^^^
...
<snip>

it happens because "-1" is returned right away instead of
doing a proper unwinding.

Fix it by jumping to "unwind" label instead of returning -1.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Closes: https://lore.kernel.org/rcu/ZxfTrHuEGtgnOYWp@pc636/T/
Fixes: 084e04fff160 ("rcuscale: Add laziness and kfree tests")
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rcu/kvfree: Fix data-race in __mod_timer / kvfree_call_rcu 2024-12-05T12:52:52+00:00 Uladzislau Rezki (Sony) urezki@gmail.com 2024-10-22T10:53:07+00:00 05b8ea1f16667f07c8e5843fb4bde3e49d49ead8 [ Upstream commit a23da88c6c80e41e0503e0b481a22c9eea63f263 ] KCSAN reports a data race when access the krcp->monitor_work.timer.expires variable in the schedule_delayed_monitor_work() function: <snip> BUG: KCSAN: data-race in __mod_timer / kvfree_call_rcu read to 0xffff888237d1cce8 of 8 bytes by task 10149 on cpu 1: schedule_delayed_monitor_work kernel/rcu/tree.c:3520 [inline] kvfree_call_rcu+0x3b8/0x510 kernel/rcu/tree.c:3839 trie_update_elem+0x47c/0x620 kernel/bpf/lpm_trie.c:441 bpf_map_update_value+0x324/0x350 kernel/bpf/syscall.c:203 generic_map_update_batch+0x401/0x520 kernel/bpf/syscall.c:1849 bpf_map_do_batch+0x28c/0x3f0 kernel/bpf/syscall.c:5143 __sys_bpf+0x2e5/0x7a0 __do_sys_bpf kernel/bpf/syscall.c:5741 [inline] __se_sys_bpf kernel/bpf/syscall.c:5739 [inline] __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5739 x64_sys_call+0x2625/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:322 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f write to 0xffff888237d1cce8 of 8 bytes by task 56 on cpu 0: __mod_timer+0x578/0x7f0 kernel/time/timer.c:1173 add_timer_global+0x51/0x70 kernel/time/timer.c:1330 __queue_delayed_work+0x127/0x1a0 kernel/workqueue.c:2523 queue_delayed_work_on+0xdf/0x190 kernel/workqueue.c:2552 queue_delayed_work include/linux/workqueue.h:677 [inline] schedule_delayed_monitor_work kernel/rcu/tree.c:3525 [inline] kfree_rcu_monitor+0x5e8/0x660 kernel/rcu/tree.c:3643 process_one_work kernel/workqueue.c:3229 [inline] process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391 kthread+0x1d1/0x210 kernel/kthread.c:389 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 56 Comm: kworker/u8:4 Not tainted 6.12.0-rc2-syzkaller-00050-g5b7c893ed5ed #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Workqueue: events_unbound kfree_rcu_monitor <snip> kfree_rcu_monitor() rearms the work if a "krcp" has to be still offloaded and this is done without holding krcp->lock, whereas the kvfree_call_rcu() holds it. Fix it by acquiring the "krcp->lock" for kfree_rcu_monitor() so both functions do not race anymore. Reported-by: syzbot+061d370693bdd99f9d34@syzkaller.appspotmail.com Link: https://lore.kernel.org/lkml/ZxZ68KmHDQYU0yfD@pc636/T/ Fixes: 8fc5494ad5fa ("rcu/kvfree: Move need_offload_krc() out of krcp->lock") Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit a23da88c6c80e41e0503e0b481a22c9eea63f263 ]

KCSAN reports a data race when access the krcp->monitor_work.timer.expires
variable in the schedule_delayed_monitor_work() function:

<snip>
BUG: KCSAN: data-race in __mod_timer / kvfree_call_rcu

read to 0xffff888237d1cce8 of 8 bytes by task 10149 on cpu 1:
 schedule_delayed_monitor_work kernel/rcu/tree.c:3520 [inline]
 kvfree_call_rcu+0x3b8/0x510 kernel/rcu/tree.c:3839
 trie_update_elem+0x47c/0x620 kernel/bpf/lpm_trie.c:441
 bpf_map_update_value+0x324/0x350 kernel/bpf/syscall.c:203
 generic_map_update_batch+0x401/0x520 kernel/bpf/syscall.c:1849
 bpf_map_do_batch+0x28c/0x3f0 kernel/bpf/syscall.c:5143
 __sys_bpf+0x2e5/0x7a0
 __do_sys_bpf kernel/bpf/syscall.c:5741 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5739 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5739
 x64_sys_call+0x2625/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888237d1cce8 of 8 bytes by task 56 on cpu 0:
 __mod_timer+0x578/0x7f0 kernel/time/timer.c:1173
 add_timer_global+0x51/0x70 kernel/time/timer.c:1330
 __queue_delayed_work+0x127/0x1a0 kernel/workqueue.c:2523
 queue_delayed_work_on+0xdf/0x190 kernel/workqueue.c:2552
 queue_delayed_work include/linux/workqueue.h:677 [inline]
 schedule_delayed_monitor_work kernel/rcu/tree.c:3525 [inline]
 kfree_rcu_monitor+0x5e8/0x660 kernel/rcu/tree.c:3643
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 56 Comm: kworker/u8:4 Not tainted 6.12.0-rc2-syzkaller-00050-g5b7c893ed5ed #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: events_unbound kfree_rcu_monitor
<snip>

kfree_rcu_monitor() rearms the work if a "krcp" has to be still
offloaded and this is done without holding krcp->lock, whereas
the kvfree_call_rcu() holds it.

Fix it by acquiring the "krcp->lock" for kfree_rcu_monitor() so
both functions do not race anymore.

Reported-by: syzbot+061d370693bdd99f9d34@syzkaller.appspotmail.com
Link: https://lore.kernel.org/lkml/ZxZ68KmHDQYU0yfD@pc636/T/
Fixes: 8fc5494ad5fa ("rcu/kvfree: Move need_offload_krc() out of krcp->lock")
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rcu/srcutiny: don't return before reenabling preemption 2024-12-05T12:52:52+00:00 Michal Schmidt mschmidt@redhat.com 2024-10-07T10:14:15+00:00 bd69a2cb7fa0af29084e55bc2be7d4d5420a4a40 [ Upstream commit 0ea3acbc804c2d5a165442cdf9c0526f4d324888 ] Code after the return statement is dead. Enable preemption before returning from srcu_drive_gp(). This will be important when/if PREEMPT_AUTO (lazy resched) gets merged. Fixes: 65b4a59557f6 ("srcu: Make Tiny SRCU explicitly disable preemption") Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Michal Schmidt <mschmidt@redhat.com> Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 0ea3acbc804c2d5a165442cdf9c0526f4d324888 ]

Code after the return statement is dead. Enable preemption before
returning from srcu_drive_gp().

This will be important when/if PREEMPT_AUTO (lazy resched) gets merged.

Fixes: 65b4a59557f6 ("srcu: Make Tiny SRCU explicitly disable preemption")
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rcu/kvfree: Refactor kvfree_rcu_queue_batch() 2024-11-08T15:31:04+00:00 Uladzislau Rezki (Sony) urezki@gmail.com 2024-09-30T11:37:10+00:00 88a470c6d2c2abc32879d39e7cad749cd47f29f3 commit 3c5d61ae919cc377c71118ccc76fa6e8518023f8 upstream. Improve readability of kvfree_rcu_queue_batch() function in away that, after a first batch queuing, the loop is break and success value is returned to a caller. There is no reason to loop and check batches further as all outstanding objects have already been picked and attached to a certain batch to complete an offloading. Fixes: 2b55d6a42d14 ("rcu/kvfree: Add kvfree_rcu_barrier() API") Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Closes: https://lore.kernel.org/lkml/ZvWUt2oyXRsvJRNc@pc636/T/ Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 3c5d61ae919cc377c71118ccc76fa6e8518023f8 upstream.

Improve readability of kvfree_rcu_queue_batch() function
in away that, after a first batch queuing, the loop is break
and success value is returned to a caller.

There is no reason to loop and check batches further as all
outstanding objects have already been picked and attached to
a certain batch to complete an offloading.

Fixes: 2b55d6a42d14 ("rcu/kvfree: Add kvfree_rcu_barrier() API")
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/lkml/ZvWUt2oyXRsvJRNc@pc636/T/
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rcu/kvfree: Add kvfree_rcu_barrier() API 2024-11-08T15:31:04+00:00 Uladzislau Rezki (Sony) urezki@gmail.com 2024-08-20T15:59:35+00:00 3cce0362ee92d089dc93ab1099e1d1c8f0dde7a5 commit 2b55d6a42d14c8675e38d6d9adca3014fdf01951 upstream. Add a kvfree_rcu_barrier() function. It waits until all in-flight pointers are freed over RCU machinery. It does not wait any GP completion and it is within its right to return immediately if there are no outstanding pointers. This function is useful when there is a need to guarantee that a memory is fully freed before destroying memory caches. For example, during unloading a kernel module. Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 2b55d6a42d14c8675e38d6d9adca3014fdf01951 upstream.

Add a kvfree_rcu_barrier() function. It waits until all
in-flight pointers are freed over RCU machinery. It does
not wait any GP completion and it is within its right to
return immediately if there are no outstanding pointers.

This function is useful when there is a need to guarantee
that a memory is fully freed before destroying memory caches.
For example, during unloading a kernel module.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rcu/nocb: Fix rcuog wake-up from offline softirq 2024-10-17T13:26:52+00:00 Frederic Weisbecker frederic@kernel.org 2024-10-10T16:36:09+00:00 e66b1e01f2eb3209d08122572f41f7838b79540d [ Upstream commit f7345ccc62a4b880cf76458db5f320725f28e400 ] After a CPU has set itself offline and before it eventually calls rcutree_report_cpu_dead(), there are still opportunities for callbacks to be enqueued, for example from a softirq. When that happens on NOCB, the rcuog wake-up is deferred through an IPI to an online CPU in order not to call into the scheduler and risk arming the RT-bandwidth after hrtimers have been migrated out and disabled. But performing a synchronized IPI from a softirq is buggy as reported in the following scenario: WARNING: CPU: 1 PID: 26 at kernel/smp.c:633 smp_call_function_single Modules linked in: rcutorture torture CPU: 1 UID: 0 PID: 26 Comm: migration/1 Not tainted 6.11.0-rc1-00012-g9139f93209d1 #1 Stopper: multi_cpu_stop+0x0/0x320 <- __stop_cpus+0xd0/0x120 RIP: 0010:smp_call_function_single <IRQ> swake_up_one_online __call_rcu_nocb_wake __call_rcu_common ? rcu_torture_one_read call_timer_fn __run_timers run_timer_softirq handle_softirqs irq_exit_rcu ? tick_handle_periodic sysvec_apic_timer_interrupt </IRQ> Fix this with forcing deferred rcuog wake up through the NOCB timer when the CPU is offline. The actual wake up will happen from rcutree_report_cpu_dead(). Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202409231644.4c55582d-lkp@intel.com Fixes: 9139f93209d1 ("rcu/nocb: Fix RT throttling hrtimer armed from offline CPU") Reviewed-by: "Joel Fernandes (Google)" <joel@joelfernandes.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit f7345ccc62a4b880cf76458db5f320725f28e400 ]

After a CPU has set itself offline and before it eventually calls
rcutree_report_cpu_dead(), there are still opportunities for callbacks
to be enqueued, for example from a softirq. When that happens on NOCB,
the rcuog wake-up is deferred through an IPI to an online CPU in order
not to call into the scheduler and risk arming the RT-bandwidth after
hrtimers have been migrated out and disabled.

But performing a synchronized IPI from a softirq is buggy as reported in
the following scenario:

        WARNING: CPU: 1 PID: 26 at kernel/smp.c:633 smp_call_function_single
        Modules linked in: rcutorture torture
        CPU: 1 UID: 0 PID: 26 Comm: migration/1 Not tainted 6.11.0-rc1-00012-g9139f93209d1 #1
        Stopper: multi_cpu_stop+0x0/0x320 <- __stop_cpus+0xd0/0x120
        RIP: 0010:smp_call_function_single
        <IRQ>
        swake_up_one_online
        __call_rcu_nocb_wake
        __call_rcu_common
        ? rcu_torture_one_read
        call_timer_fn
        __run_timers
        run_timer_softirq
        handle_softirqs
        irq_exit_rcu
        ? tick_handle_periodic
        sysvec_apic_timer_interrupt
        </IRQ>

Fix this with forcing deferred rcuog wake up through the NOCB timer when
the CPU is offline. The actual wake up will happen from
rcutree_report_cpu_dead().

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202409231644.4c55582d-lkp@intel.com
Fixes: 9139f93209d1 ("rcu/nocb: Fix RT throttling hrtimer armed from offline CPU")
Reviewed-by: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rcuscale: Provide clear error when async specified without primitives 2024-10-10T10:03:22+00:00 Paul E. McKenney paulmck@kernel.org 2024-08-02T00:43:03+00:00 d175fd93cc8512c4814e14010d96f78cc49d2c37 [ Upstream commit 11377947b5861fa59bf77c827e1dd7c081842cc9 ] Currently, if the rcuscale module's async module parameter is specified for RCU implementations that do not have async primitives such as RCU Tasks Rude (which now lacks a call_rcu_tasks_rude() function), there will be a series of splats due to calls to a NULL pointer. This commit therefore warns of this situation, but switches to non-async testing. Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 11377947b5861fa59bf77c827e1dd7c081842cc9 ]

Currently, if the rcuscale module's async module parameter is specified
for RCU implementations that do not have async primitives such as RCU
Tasks Rude (which now lacks a call_rcu_tasks_rude() function), there
will be a series of splats due to calls to a NULL pointer.  This commit
therefore warns of this situation, but switches to non-async testing.

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rcu-tasks: Fix access non-existent percpu rtpcp variable in rcu_tasks_need_gpcb() 2024-10-10T10:03:21+00:00 Zqiang qiang.zhang1211@gmail.com 2024-07-10T04:45:42+00:00 05095271a4fb0f6497121a057f9a2edf386d5d96 [ Upstream commit fd70e9f1d85f5323096ad313ba73f5fe3d15ea41 ] 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: smpboot: Allowing 4 CPUs, 0 hotplug CPUs ... setup_percpu: NR_CPUS:512 nr_cpumask_bits:512 nr_cpu_ids:512 nr_node_ids:1 ... BUG: unable to handle page fault for address: ffffffff9911c8c8 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 15 Comm: rcu_tasks_trace Tainted: G W 6.6.21 #1 5dc7acf91a5e8e9ac9dcfc35bee0245691283ea6 RIP: 0010:rcu_tasks_need_gpcb+0x25d/0x2c0 RSP: 0018:ffffa371c00a3e60 EFLAGS: 00010082 CR2: ffffffff9911c8c8 CR3: 000000040fa20005 CR4: 00000000001706f0 Call Trace: <TASK> ? __die+0x23/0x80 ? page_fault_oops+0xa4/0x180 ? exc_page_fault+0x152/0x180 ? asm_exc_page_fault+0x26/0x40 ? rcu_tasks_need_gpcb+0x25d/0x2c0 ? __pfx_rcu_tasks_kthread+0x40/0x40 rcu_tasks_one_gp+0x69/0x180 rcu_tasks_kthread+0x94/0xc0 kthread+0xe8/0x140 ? __pfx_kthread+0x40/0x40 ret_from_fork+0x34/0x80 ? __pfx_kthread+0x40/0x40 ret_from_fork_asm+0x1b/0x80 </TASK> Considering that there may be holes in the CPU numbers, use the maximum possible cpu number, instead of nr_cpu_ids, for configuring enqueue and dequeue limits. [ neeraj.upadhyay: Fix htmldocs build error reported by Stephen Rothwell ] Closes: https://lore.kernel.org/linux-input/CALMA0xaTSMN+p4xUXkzrtR5r6k7hgoswcaXx7baR_z9r5jjskw@mail.gmail.com/T/#u Reported-by: Zhixu Liu <zhixu.liu@gmail.com> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit fd70e9f1d85f5323096ad313ba73f5fe3d15ea41 ]

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:

smpboot: Allowing 4 CPUs, 0 hotplug CPUs
...
setup_percpu: NR_CPUS:512 nr_cpumask_bits:512 nr_cpu_ids:512 nr_node_ids:1
...
BUG: unable to handle page fault for address: ffffffff9911c8c8
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 0 PID: 15 Comm: rcu_tasks_trace Tainted: G W
6.6.21 #1 5dc7acf91a5e8e9ac9dcfc35bee0245691283ea6
RIP: 0010:rcu_tasks_need_gpcb+0x25d/0x2c0
RSP: 0018:ffffa371c00a3e60 EFLAGS: 00010082
CR2: ffffffff9911c8c8 CR3: 000000040fa20005 CR4: 00000000001706f0
Call Trace:
<TASK>
? __die+0x23/0x80
? page_fault_oops+0xa4/0x180
? exc_page_fault+0x152/0x180
? asm_exc_page_fault+0x26/0x40
? rcu_tasks_need_gpcb+0x25d/0x2c0
? __pfx_rcu_tasks_kthread+0x40/0x40
rcu_tasks_one_gp+0x69/0x180
rcu_tasks_kthread+0x94/0xc0
kthread+0xe8/0x140
? __pfx_kthread+0x40/0x40
ret_from_fork+0x34/0x80
? __pfx_kthread+0x40/0x40
ret_from_fork_asm+0x1b/0x80
</TASK>

Considering that there may be holes in the CPU numbers, use the
maximum possible cpu number, instead of nr_cpu_ids, for configuring
enqueue and dequeue limits.

[ neeraj.upadhyay: Fix htmldocs build error reported by Stephen Rothwell ]

Closes: https://lore.kernel.org/linux-input/CALMA0xaTSMN+p4xUXkzrtR5r6k7hgoswcaXx7baR_z9r5jjskw@mail.gmail.com/T/#u
Reported-by: Zhixu Liu <zhixu.liu@gmail.com>
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rcu/nocb: Fix RT throttling hrtimer armed from offline CPU 2024-10-04T14:37:42+00:00 Frederic Weisbecker frederic@kernel.org 2024-08-13T22:56:40+00:00 00a611229bfad075660181c53e054ff544d3ac34 [ Upstream commit 9139f93209d1ffd7f489ab19dee01b7c3a1a43d2 ] After a CPU is marked offline and until it reaches its final trip to idle, rcuo has several opportunities to be woken up, either because a callback has been queued in the meantime or because rcutree_report_cpu_dead() has issued the final deferred NOCB wake up. If RCU-boosting is enabled, RCU kthreads are set to SCHED_FIFO policy. And if RT-bandwidth is enabled, the related hrtimer might be armed. However this then happens after hrtimers have been migrated at the CPUHP_AP_HRTIMERS_DYING stage, which is broken as reported by the following warning: Call trace: enqueue_hrtimer+0x7c/0xf8 hrtimer_start_range_ns+0x2b8/0x300 enqueue_task_rt+0x298/0x3f0 enqueue_task+0x94/0x188 ttwu_do_activate+0xb4/0x27c try_to_wake_up+0x2d8/0x79c wake_up_process+0x18/0x28 __wake_nocb_gp+0x80/0x1a0 do_nocb_deferred_wakeup_common+0x3c/0xcc rcu_report_dead+0x68/0x1ac cpuhp_report_idle_dead+0x48/0x9c do_idle+0x288/0x294 cpu_startup_entry+0x34/0x3c secondary_start_kernel+0x138/0x158 Fix this with waking up rcuo using an IPI if necessary. Since the existing API to deal with this situation only handles swait queue, rcuo is only woken up from offline CPUs if it's not already waiting on a grace period. In the worst case some callbacks will just wait for a grace period to complete before being assigned to a subsequent one. Reported-by: "Cheng-Jui Wang (王正睿)" <Cheng-Jui.Wang@mediatek.com> Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier") Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 9139f93209d1ffd7f489ab19dee01b7c3a1a43d2 ]

After a CPU is marked offline and until it reaches its final trip to
idle, rcuo has several opportunities to be woken up, either because
a callback has been queued in the meantime or because
rcutree_report_cpu_dead() has issued the final deferred NOCB wake up.

If RCU-boosting is enabled, RCU kthreads are set to SCHED_FIFO policy.
And if RT-bandwidth is enabled, the related hrtimer might be armed.
However this then happens after hrtimers have been migrated at the
CPUHP_AP_HRTIMERS_DYING stage, which is broken as reported by the
following warning:

 Call trace:
  enqueue_hrtimer+0x7c/0xf8
  hrtimer_start_range_ns+0x2b8/0x300
  enqueue_task_rt+0x298/0x3f0
  enqueue_task+0x94/0x188
  ttwu_do_activate+0xb4/0x27c
  try_to_wake_up+0x2d8/0x79c
  wake_up_process+0x18/0x28
  __wake_nocb_gp+0x80/0x1a0
  do_nocb_deferred_wakeup_common+0x3c/0xcc
  rcu_report_dead+0x68/0x1ac
  cpuhp_report_idle_dead+0x48/0x9c
  do_idle+0x288/0x294
  cpu_startup_entry+0x34/0x3c
  secondary_start_kernel+0x138/0x158

Fix this with waking up rcuo using an IPI if necessary. Since the
existing API to deal with this situation only handles swait queue, rcuo
is only woken up from offline CPUs if it's not already waiting on a
grace period. In the worst case some callbacks will just wait for a
grace period to complete before being assigned to a subsequent one.

Reported-by: "Cheng-Jui Wang (王正睿)" <Cheng-Jui.Wang@mediatek.com>
Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Merge branches 'doc.2024.06.06a', 'fixes.2024.07.04a', 'mb.2024.06.28a', 'nocb.2024.06.03a', 'rcu-tasks.2024.06.06a', 'rcutorture.2024.06.06a' and 'srcu.2024.06.18a' into HEAD 2024-07-04T20:54:17+00:00 Paul E. McKenney paulmck@kernel.org 2024-07-04T20:54:17+00:00 02219caa92b5b0ed97f8d8b9cf580f6f34a9be31 doc.2024.06.06a: Documentation updates. fixes.2024.07.04a: Miscellaneous fixes. mb.2024.06.28a: Grace-period memory-barrier redundancy removal. nocb.2024.06.03a: No-CB CPU updates. rcu-tasks.2024.06.06a: RCU-Tasks updates. rcutorture.2024.06.06a: Torture-test updates. srcu.2024.06.18a: SRCU polled-grace-period updates. 
doc.2024.06.06a: Documentation updates.
fixes.2024.07.04a: Miscellaneous fixes.
mb.2024.06.28a: Grace-period memory-barrier redundancy removal.
nocb.2024.06.03a: No-CB CPU updates.
rcu-tasks.2024.06.06a: RCU-Tasks updates.
rcutorture.2024.06.06a: Torture-test updates.
srcu.2024.06.18a: SRCU polled-grace-period updates.