Enabling SMP support? #252
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Isn't that wrong? lkl heavily uses threads for syscalls, kthreads, etc. |
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@M1cha What Jerry is saying is that we can only run one system call at a time, which, on multi processor systems is limiting the amount of work we can do with one instance. @hkchu some of the work I did for #246 has multiple CPU support in mind (see the "CPU access" patch), although I don't have a strict timeline in mind. The next item on my TODO list is user level threads (for hosts such as UEFI), multi processor support, module support. |
thehajime
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Nov 8, 2017
commit 656d61c upstream. printk_ratelimit() invokes ___ratelimit() which may invoke a normal printk() (pr_warn() in this particular case) to warn about suppressed output. Given that printk_ratelimit() may be called from anywhere, that pr_warn() is dangerous - it may end up deadlocking the system. Fix ___ratelimit() by using deferred printk(). Sasha reported the following lockdep error: : Unregister pv shared memory for cpu 8 : select_fallback_rq: 3 callbacks suppressed : process 8583 (trinity-c78) no longer affine to cpu8 : : ====================================================== : WARNING: possible circular locking dependency detected : 4.14.0-rc2-next-20170927+ lkl#252 Not tainted : ------------------------------------------------------ : migration/8/62 is trying to acquire lock: : (&port_lock_key){-.-.}, at: serial8250_console_write() : : but task is already holding lock: : (&rq->lock){-.-.}, at: sched_cpu_dying() : : which lock already depends on the new lock. : : : the existing dependency chain (in reverse order) is: : : -> #3 (&rq->lock){-.-.}: : __lock_acquire() : lock_acquire() : _raw_spin_lock() : task_fork_fair() : sched_fork() : copy_process.part.31() : _do_fork() : kernel_thread() : rest_init() : start_kernel() : x86_64_start_reservations() : x86_64_start_kernel() : verify_cpu() : : -> #2 (&p->pi_lock){-.-.}: : __lock_acquire() : lock_acquire() : _raw_spin_lock_irqsave() : try_to_wake_up() : default_wake_function() : woken_wake_function() : __wake_up_common() : __wake_up_common_lock() : __wake_up() : tty_wakeup() : tty_port_default_wakeup() : tty_port_tty_wakeup() : uart_write_wakeup() : serial8250_tx_chars() : serial8250_handle_irq.part.25() : serial8250_default_handle_irq() : serial8250_interrupt() : __handle_irq_event_percpu() : handle_irq_event_percpu() : handle_irq_event() : handle_level_irq() : handle_irq() : do_IRQ() : ret_from_intr() : native_safe_halt() : default_idle() : arch_cpu_idle() : default_idle_call() : do_idle() : cpu_startup_entry() : rest_init() : start_kernel() : x86_64_start_reservations() : x86_64_start_kernel() : verify_cpu() : : -> #1 (&tty->write_wait){-.-.}: : __lock_acquire() : lock_acquire() : _raw_spin_lock_irqsave() : __wake_up_common_lock() : __wake_up() : tty_wakeup() : tty_port_default_wakeup() : tty_port_tty_wakeup() : uart_write_wakeup() : serial8250_tx_chars() : serial8250_handle_irq.part.25() : serial8250_default_handle_irq() : serial8250_interrupt() : __handle_irq_event_percpu() : handle_irq_event_percpu() : handle_irq_event() : handle_level_irq() : handle_irq() : do_IRQ() : ret_from_intr() : native_safe_halt() : default_idle() : arch_cpu_idle() : default_idle_call() : do_idle() : cpu_startup_entry() : rest_init() : start_kernel() : x86_64_start_reservations() : x86_64_start_kernel() : verify_cpu() : : -> #0 (&port_lock_key){-.-.}: : check_prev_add() : __lock_acquire() : lock_acquire() : _raw_spin_lock_irqsave() : serial8250_console_write() : univ8250_console_write() : console_unlock() : vprintk_emit() : vprintk_default() : vprintk_func() : printk() : ___ratelimit() : __printk_ratelimit() : select_fallback_rq() : sched_cpu_dying() : cpuhp_invoke_callback() : take_cpu_down() : multi_cpu_stop() : cpu_stopper_thread() : smpboot_thread_fn() : kthread() : ret_from_fork() : : other info that might help us debug this: : : Chain exists of: : &port_lock_key --> &p->pi_lock --> &rq->lock : : Possible unsafe locking scenario: : : CPU0 CPU1 : ---- ---- : lock(&rq->lock); : lock(&p->pi_lock); : lock(&rq->lock); : lock(&port_lock_key); : : *** DEADLOCK *** : : 4 locks held by migration/8/62: : #0: (&p->pi_lock){-.-.}, at: sched_cpu_dying() : #1: (&rq->lock){-.-.}, at: sched_cpu_dying() : #2: (printk_ratelimit_state.lock){....}, at: ___ratelimit() : #3: (console_lock){+.+.}, at: vprintk_emit() : : stack backtrace: : CPU: 8 PID: 62 Comm: migration/8 Not tainted 4.14.0-rc2-next-20170927+ lkl#252 : Call Trace: : dump_stack() : print_circular_bug() : check_prev_add() : ? add_lock_to_list.isra.26() : ? check_usage() : ? kvm_clock_read() : ? kvm_sched_clock_read() : ? sched_clock() : ? check_preemption_disabled() : __lock_acquire() : ? __lock_acquire() : ? add_lock_to_list.isra.26() : ? debug_check_no_locks_freed() : ? memcpy() : lock_acquire() : ? serial8250_console_write() : _raw_spin_lock_irqsave() : ? serial8250_console_write() : serial8250_console_write() : ? serial8250_start_tx() : ? lock_acquire() : ? memcpy() : univ8250_console_write() : console_unlock() : ? __down_trylock_console_sem() : vprintk_emit() : vprintk_default() : vprintk_func() : printk() : ? show_regs_print_info() : ? lock_acquire() : ___ratelimit() : __printk_ratelimit() : select_fallback_rq() : sched_cpu_dying() : ? sched_cpu_starting() : ? rcutree_dying_cpu() : ? sched_cpu_starting() : cpuhp_invoke_callback() : ? cpu_disable_common() : take_cpu_down() : ? trace_hardirqs_off_caller() : ? cpuhp_invoke_callback() : multi_cpu_stop() : ? __this_cpu_preempt_check() : ? cpu_stop_queue_work() : cpu_stopper_thread() : ? cpu_stop_create() : smpboot_thread_fn() : ? sort_range() : ? schedule() : ? __kthread_parkme() : kthread() : ? sort_range() : ? kthread_create_on_node() : ret_from_fork() : process 9121 (trinity-c78) no longer affine to cpu8 : smpboot: CPU 8 is now offline Link: http://lkml.kernel.org/r/20170928120405.18273-1-sergey.senozhatsky@gmail.com Fixes: 6b1d174 ("ratelimit: extend to print suppressed messages on release") Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reported-by: Sasha Levin <levinsasha928@gmail.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Borislav Petkov <bp@suse.de> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rodionov
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Jan 2, 2025
Add a new test case which performs double query of the bpf_mprog through libbpf API, but also via raw bpf(2) syscall. This is testing to gather first the count and then in a subsequent probe the full information with the program array without clearing passed structs in between. # ./vmtest.sh -- ./test_progs -t tc_opts [...] ./test_progs -t tc_opts [ 1.398818] tsc: Refined TSC clocksource calibration: 3407.999 MHz [ 1.400263] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fd336761, max_idle_ns: 440795243819 ns [ 1.402734] clocksource: Switched to clocksource tsc [ 1.426639] bpf_testmod: loading out-of-tree module taints kernel. [ 1.428112] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel lkl#252 tc_opts_after:OK lkl#253 tc_opts_append:OK lkl#254 tc_opts_basic:OK lkl#255 tc_opts_before:OK lkl#256 tc_opts_chain_classic:OK lkl#257 tc_opts_chain_mixed:OK lkl#258 tc_opts_delete_empty:OK lkl#259 tc_opts_demixed:OK lkl#260 tc_opts_detach:OK lkl#261 tc_opts_detach_after:OK lkl#262 tc_opts_detach_before:OK lkl#263 tc_opts_dev_cleanup:OK lkl#264 tc_opts_invalid:OK lkl#265 tc_opts_max:OK lkl#266 tc_opts_mixed:OK lkl#267 tc_opts_prepend:OK lkl#268 tc_opts_query:OK <--- (new test) lkl#269 tc_opts_replace:OK lkl#270 tc_opts_revision:OK Summary: 19/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/r/20231006220655.1653-4-daniel@iogearbox.net Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
rodionov
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Add a new test case to query on an empty bpf_mprog and pass the revision directly into expected_revision for attachment to assert that this does succeed. ./test_progs -t tc_opts [ 1.406778] tsc: Refined TSC clocksource calibration: 3407.990 MHz [ 1.408863] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fcaf6eb0, max_idle_ns: 440795321766 ns [ 1.412419] clocksource: Switched to clocksource tsc [ 1.428671] bpf_testmod: loading out-of-tree module taints kernel. [ 1.430260] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel lkl#252 tc_opts_after:OK lkl#253 tc_opts_append:OK lkl#254 tc_opts_basic:OK lkl#255 tc_opts_before:OK lkl#256 tc_opts_chain_classic:OK lkl#257 tc_opts_chain_mixed:OK lkl#258 tc_opts_delete_empty:OK lkl#259 tc_opts_demixed:OK lkl#260 tc_opts_detach:OK lkl#261 tc_opts_detach_after:OK lkl#262 tc_opts_detach_before:OK lkl#263 tc_opts_dev_cleanup:OK lkl#264 tc_opts_invalid:OK lkl#265 tc_opts_max:OK lkl#266 tc_opts_mixed:OK lkl#267 tc_opts_prepend:OK lkl#268 tc_opts_query:OK lkl#269 tc_opts_query_attach:OK <--- (new test) lkl#270 tc_opts_replace:OK lkl#271 tc_opts_revision:OK Summary: 20/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/r/20231006220655.1653-6-daniel@iogearbox.net Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
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LKL is currently single threaded. Does anyone know or have experience enabling SMP on an arch port like LKL? We may have use cases in the near future that requires performance attainable only through the parallel use of multiple CPUs and I wonder how easy/difficult this work may be.
Thanks.
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