[ Upstream commit 668c0406d887467d53f8fe79261dda1d22d5b671 ] When the torture_type is set srcu or srcud and cb_barrier is non-zero, running the rcutorture test will trigger the following warning: [ 163.910989][ C1] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 [ 163.910994][ C1] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1 [ 163.910999][ C1] preempt_count: 10001, expected: 0 [ 163.911002][ C1] RCU nest depth: 0, expected: 0 [ 163.911005][ C1] INFO: lockdep is turned off. [ 163.911007][ C1] irq event stamp: 30964 [ 163.911010][ C1] hardirqs last enabled at (30963): [<ffffffffabc7df52>] do_idle+0x362/0x500 [ 163.911018][ C1] hardirqs last disabled at (30964): [<ffffffffae616eff>] sysvec_call_function_single+0xf/0xd0 [ 163.911025][ C1] softirqs last enabled at (0): [<ffffffffabb6475f>] copy_process+0x16ff/0x6580 [ 163.911033][ C1] softirqs last disabled at (0): [<0000000000000000>] 0x0 [ 163.911038][ C1] Preemption disabled at: [ 163.911039][ C1] [<ffffffffacf1964b>] stack_depot_save_flags+0x24b/0x6c0 [ 163.911063][ C1] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 6.8.0-rc4-rt4-yocto-preempt-rt+ #3 1e39aa9a737dd024a3275c4f835a872f673a7d3a [ 163.911071][ C1] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [ 163.911075][ C1] Call Trace: [ 163.911078][ C1] <IRQ> [ 163.911080][ C1] dump_stack_lvl+0x88/0xd0 [ 163.911089][ C1] dump_stack+0x10/0x20 [ 163.911095][ C1] __might_resched+0x36f/0x530 [ 163.911105][ C1] rt_spin_lock+0x82/0x1c0 [ 163.911112][ C1] spin_lock_irqsave_ssp_contention+0xb8/0x100 [ 163.911121][ C1] srcu_gp_start_if_needed+0x782/0xf00 [ 163.911128][ C1] ? _raw_spin_unlock_irqrestore+0x46/0x70 [ 163.911136][ C1] ? debug_object_active_state+0x336/0x470 [ 163.911148][ C1] ? __pfx_srcu_gp_start_if_needed+0x10/0x10 [ 163.911156][ C1] ? __pfx_lock_release+0x10/0x10 [ 163.911165][ C1] ? __pfx_rcu_torture_barrier_cbf+0x10/0x10 [ 163.911188][ C1] __call_srcu+0x9f/0xe0 [ 163.911196][ C1] call_srcu+0x13/0x20 [ 163.911201][ C1] srcu_torture_call+0x1b/0x30 [ 163.911224][ C1] rcu_torture_barrier1cb+0x4a/0x60 [ 163.911247][ C1] __flush_smp_call_function_queue+0x267/0xca0 [ 163.911256][ C1] ? __pfx_rcu_torture_barrier1cb+0x10/0x10 [ 163.911281][ C1] generic_smp_call_function_single_interrupt+0x13/0x20 [ 163.911288][ C1] __sysvec_call_function_single+0x7d/0x280 [ 163.911295][ C1] sysvec_call_function_single+0x93/0xd0 [ 163.911302][ C1] </IRQ> [ 163.911304][ C1] <TASK> [ 163.911308][ C1] asm_sysvec_call_function_single+0x1b/0x20 [ 163.911313][ C1] RIP: 0010:default_idle+0x17/0x20 [ 163.911326][ C1] RSP: 0018:ffff888001997dc8 EFLAGS: 00000246 [ 163.911333][ C1] RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffffae618b51 [ 163.911337][ C1] RDX: 0000000000000000 RSI: ffffffffaea80920 RDI: ffffffffaec2de80 [ 163.911342][ C1] RBP: ffff888001997dc8 R08: 0000000000000001 R09: ffffed100d740cad [ 163.911346][ C1] R10: ffffed100d740cac R11: ffff88806ba06563 R12: 0000000000000001 [ 163.911350][ C1] R13: ffffffffafe460c0 R14: ffffffffafe460c0 R15: 0000000000000000 [ 163.911358][ C1] ? ct_kernel_exit.constprop.3+0x121/0x160 [ 163.911369][ C1] ? lockdep_hardirqs_on+0xc4/0x150 [ 163.911376][ C1] arch_cpu_idle+0x9/0x10 [ 163.911383][ C1] default_idle_call+0x7a/0xb0 [ 163.911390][ C1] do_idle+0x362/0x500 [ 163.911398][ C1] ? __pfx_do_idle+0x10/0x10 [ 163.911404][ C1] ? complete_with_flags+0x8b/0xb0 [ 163.911416][ C1] cpu_startup_entry+0x58/0x70 [ 163.911423][ C1] start_secondary+0x221/0x280 [ 163.911430][ C1] ? __pfx_start_secondary+0x10/0x10 [ 163.911440][ C1] secondary_startup_64_no_verify+0x17f/0x18b [ 163.911455][ C1] </TASK> This commit therefore use smp_call_on_cpu() instead of smp_call_function_single(), make rcu_torture_barrier1cb() invoked happens on task-context. Signed-off-by: Zqiang <qiang.zhang1211@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 431315a563015f259b28e34c5842f6166439e969 ] When the rcutorture tests start to exit, the rcu_torture_cleanup() is invoked to stop kthreads and release resources, if the stall-task kthreads exist, cpu-stall has started and the rcutorture.stall_cpu is set to a larger value, the rcu_torture_cleanup() will be blocked for a long time and the hung-task may occur, this commit therefore add kthread_should_stop() to the loop of cpu-stall operation, when rcutorture tests ends, no need to wait for cpu-stall to end, exit directly. Use the following command to test: insmod rcutorture.ko torture_type=srcu fwd_progress=0 stat_interval=4 stall_cpu_block=1 stall_cpu=200 stall_cpu_holdoff=10 read_exit_burst=0 object_debug=1 rmmod rcutorture [15361.918610] INFO: task rmmod:878 blocked for more than 122 seconds. [15361.918613] Tainted: G W 6.8.0-rc2-yoctodev-standard+ #25 [15361.918615] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [15361.918616] task:rmmod state:D stack:0 pid:878 tgid:878 ppid:773 flags:0x00004002 [15361.918621] Call Trace: [15361.918623] <TASK> [15361.918626] __schedule+0xc0d/0x28f0 [15361.918631] ? __pfx___schedule+0x10/0x10 [15361.918635] ? rcu_is_watching+0x19/0xb0 [15361.918638] ? schedule+0x1f6/0x290 [15361.918642] ? __pfx_lock_release+0x10/0x10 [15361.918645] ? schedule+0xc9/0x290 [15361.918648] ? schedule+0xc9/0x290 [15361.918653] ? trace_preempt_off+0x54/0x100 [15361.918657] ? schedule+0xc9/0x290 [15361.918661] schedule+0xd0/0x290 [15361.918665] schedule_timeout+0x56d/0x7d0 [15361.918669] ? debug_smp_processor_id+0x1b/0x30 [15361.918672] ? rcu_is_watching+0x19/0xb0 [15361.918676] ? __pfx_schedule_timeout+0x10/0x10 [15361.918679] ? debug_smp_processor_id+0x1b/0x30 [15361.918683] ? rcu_is_watching+0x19/0xb0 [15361.918686] ? wait_for_completion+0x179/0x4c0 [15361.918690] ? __pfx_lock_release+0x10/0x10 [15361.918693] ? __kasan_check_write+0x18/0x20 [15361.918696] ? wait_for_completion+0x9d/0x4c0 [15361.918700] ? _raw_spin_unlock_irq+0x36/0x50 [15361.918703] ? wait_for_completion+0x179/0x4c0 [15361.918707] ? _raw_spin_unlock_irq+0x36/0x50 [15361.918710] ? wait_for_completion+0x179/0x4c0 [15361.918714] ? trace_preempt_on+0x54/0x100 [15361.918718] ? wait_for_completion+0x179/0x4c0 [15361.918723] wait_for_completion+0x181/0x4c0 [15361.918728] ? __pfx_wait_for_completion+0x10/0x10 [15361.918738] kthread_stop+0x152/0x470 [15361.918742] _torture_stop_kthread+0x44/0xc0 [torture 7af7f9cbba28271a10503b653f9e05d518fbc8c3] [15361.918752] rcu_torture_cleanup+0x2ac/0xe90 [rcutorture f2cb1f556ee7956270927183c4c2c7749a336529] [15361.918766] ? __pfx_rcu_torture_cleanup+0x10/0x10 [rcutorture f2cb1f556ee7956270927183c4c2c7749a336529] [15361.918777] ? __kasan_check_write+0x18/0x20 [15361.918781] ? __mutex_unlock_slowpath+0x17c/0x670 [15361.918789] ? __might_fault+0xcd/0x180 [15361.918793] ? find_module_all+0x104/0x1d0 [15361.918799] __x64_sys_delete_module+0x2a4/0x3f0 [15361.918803] ? __pfx___x64_sys_delete_module+0x10/0x10 [15361.918807] ? syscall_exit_to_user_mode+0x149/0x280 Signed-off-by: Zqiang <qiang.zhang1211@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 8b9b443fa860276822b25057cb3ff3b28734dec0 ] The "pipe_count > RCU_TORTURE_PIPE_LEN" check has a comment saying "Should not happen, but...". This is only true when testing an RCU whose grace periods are always long enough. This commit therefore fixes this comment. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Closes: https://lore.kernel.org/lkml/CAHk-=wi7rJ-eGq+xaxVfzFEgbL9tdf6Kc8Z89rCpfcQOKm74Tw@mail.gmail.com/ Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 3758f7d9917bd7ef0482c4184c0ad673b4c4e069 ]
The rcuc-starvation output from print_cpu_stall_info() might overflow the
buffer if there is a huge difference in jiffies difference. The situation
might seem improbable, but computers sometimes get very confused about
time, which can result in full-sized integers, and, in this case,
buffer overflow.
Also, the unsigned jiffies difference is printed using %ld, which is
normally for signed integers. This is intentional for debugging purposes,
but it is not obvious from the code.
This commit therefore changes sprintf() to snprintf() and adds a
clarifying comment about intention of %ld format.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: 245a62982502 ("rcu: Dump rcuc kthread status for CPUs not reporting quiescent state")
Signed-off-by: Nikita Kiryushin <kiryushin@ancud.ru>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit cc5645fddb0ce28492b15520306d092730dffa48 ]
There is a possibility of buffer overflow in
show_rcu_tasks_trace_gp_kthread() if counters, passed
to sprintf() are huge. Counter numbers, needed for this
are unrealistically high, but buffer overflow is still
possible.
Use snprintf() with buffer size instead of sprintf().
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: edf3775f0ad6 ("rcu-tasks: Add count for idle tasks on offline CPUs")
Signed-off-by: Nikita Kiryushin <kiryushin@ancud.ru>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
The current code will scan the entirety of each per-CPU list of exiting tasks in ->rtp_exit_list with interrupts disabled. This is normally just fine, because each CPU typically won't have very many tasks in this state. However, if a large number of tasks block late in do_exit(), these lists could be arbitrarily long. Low probability, perhaps, but it really could happen. This commit therefore occasionally re-enables interrupts while traversing these lists, inserting a dummy element to hold the current place in the list. In kernels built with CONFIG_PREEMPT_RT=y, this re-enabling happens after each list element is processed, otherwise every one-to-two jiffies. [ paulmck: Apply Frederic Weisbecker feedback. ] Link: https://lore.kernel.org/all/ZdeI_-RfdLR8jlsm@localhost.localdomain/ Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Anna-Maria Behnsen <anna-maria@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Holding a mutex across synchronize_rcu_tasks() and acquiring that same mutex in code called from do_exit() after its call to exit_tasks_rcu_start() but before its call to exit_tasks_rcu_stop() results in deadlock. This is by design, because tasks that are far enough into do_exit() are no longer present on the tasks list, making it a bit difficult for RCU Tasks to find them, let alone wait on them to do a voluntary context switch. However, such deadlocks are becoming more frequent. In addition, lockdep currently does not detect such deadlocks and they can be difficult to reproduce. In addition, if a task voluntarily context switches during that time (for example, if it blocks acquiring a mutex), then this task is in an RCU Tasks quiescent state. And with some adjustments, RCU Tasks could just as well take advantage of that fact. This commit therefore eliminates these deadlock by replacing the SRCU-based wait for do_exit() completion with per-CPU lists of tasks currently exiting. A given task will be on one of these per-CPU lists for the same period of time that this task would previously have been in the previous SRCU read-side critical section. These lists enable RCU Tasks to find the tasks that have already been removed from the tasks list, but that must nevertheless be waited upon. The RCU Tasks grace period gathers any of these do_exit() tasks that it must wait on, and adds them to the list of holdouts. Per-CPU locking and get_task_struct() are used to synchronize addition to and removal from these lists. Link: https://lore.kernel.org/all/20240118021842.290665-1-chenzhongjin@huawei.com/ Reported-by: Chen Zhongjin <chenzhongjin@huawei.com> Reported-by: Yang Jihong <yangjihong1@huawei.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Tested-by: Yang Jihong <yangjihong1@huawei.com> Tested-by: Chen Zhongjin <chenzhongjin@huawei.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit continues the elimination of deadlocks involving do_exit() and RCU tasks by causing exit_tasks_rcu_start() to add the current task to a per-CPU list and causing exit_tasks_rcu_stop() to remove the current task from whatever list it is on. These lists will be used to track tasks that are exiting, while still accounting for any RCU-tasks quiescent states that these tasks pass though. [ paulmck: Apply Frederic Weisbecker feedback. ] Link: https://lore.kernel.org/all/20240118021842.290665-1-chenzhongjin@huawei.com/ Reported-by: Chen Zhongjin <chenzhongjin@huawei.com> Reported-by: Yang Jihong <yangjihong1@huawei.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Tested-by: Yang Jihong <yangjihong1@huawei.com> Tested-by: Chen Zhongjin <chenzhongjin@huawei.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Holding a mutex across synchronize_rcu_tasks() and acquiring that same mutex in code called from do_exit() after its call to exit_tasks_rcu_start() but before its call to exit_tasks_rcu_stop() results in deadlock. This is by design, because tasks that are far enough into do_exit() are no longer present on the tasks list, making it a bit difficult for RCU Tasks to find them, let alone wait on them to do a voluntary context switch. However, such deadlocks are becoming more frequent. In addition, lockdep currently does not detect such deadlocks and they can be difficult to reproduce. In addition, if a task voluntarily context switches during that time (for example, if it blocks acquiring a mutex), then this task is in an RCU Tasks quiescent state. And with some adjustments, RCU Tasks could just as well take advantage of that fact. This commit therefore initializes the data structures that will be needed to rely on these quiescent states and to eliminate these deadlocks. Link: https://lore.kernel.org/all/20240118021842.290665-1-chenzhongjin@huawei.com/ Reported-by: Chen Zhongjin <chenzhongjin@huawei.com> Reported-by: Yang Jihong <yangjihong1@huawei.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Tested-by: Yang Jihong <yangjihong1@huawei.com> Tested-by: Chen Zhongjin <chenzhongjin@huawei.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>