On 14.10.2021 11:20, Cyrill Gorcunov wrote:
> The @cpu_flags_lock spinlock guards manipulations with
> per-cpu @cpu_flags which is used to hide some features
> in cpuinfo output inside VE. Still the init_cpu_flags
> is called from irq context leading to the following
>
> | [ 13.827635] =============================
> | [ 13.827636] [ BUG: Invalid wait context ]
> | [ 13.827637] 5.14.0.ovz9.10.1+ #41 Tainted: G C X ---------
> ---
> | [ 13.827638] -----------------------------
> | [ 13.827638] systemd/1 is trying to lock:
> | [ 13.827639] ffffffffa4c9d258 (cpu_flags_lock){....}-{3:3}, at:
> init_cpu_flags+0xc8/0x220
> | [ 13.827649] other info that might help us debug this:
> | [ 13.827651] context-{2:2}
> | [ 13.827651] 3 locks held by systemd/1:
> | [ 13.827652] #0: ffffffffa56e8c60 (dup_mmap_sem){.+.+}-{0:0}, at:
> dup_mm+0x83/0x5f0
> | [ 13.827660] #1: ffff97574a37d138 (&mm->mmap_lock#2){++++}-{4:4}, at:
> dup_mm+0x9c/0x5f0
> | [ 13.827664] #2: ffff97574489c138 (&mm->mmap_lock/1){+.+.}-{4:4}, at:
> dup_mm+0xd5/0x5f0
> | [ 13.827667] stack backtrace:
> | [ 13.827668] CPU: 0 PID: 1 Comm: systemd ve: / Tainted: G C
> X --------- ---
> | [ 13.827670] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> 1.14.0-4.fc34 04/01/2014
> | [ 13.827672] Call Trace:
> | [ 13.827673] <IRQ>
> | [ 13.827675] dump_stack_lvl+0x57/0x7d
> | [ 13.827686] __lock_acquire.cold+0x28b/0x2cd
> | [ 13.827694] lock_acquire+0xca/0x300
> | [ 13.827700] ? init_cpu_flags+0xc8/0x220
> | [ 13.827703] _raw_spin_lock+0x34/0x80
> | [ 13.827708] ? init_cpu_flags+0xc8/0x220
> | [ 13.827710] init_cpu_flags+0xc8/0x220
> | [ 13.827713] flush_smp_call_function_queue+0x13f/0x1e0
> | [ 13.827717] __sysvec_call_function_single+0x43/0x1c0
> | [ 13.827722] sysvec_call_function_single+0x9d/0xd0
> | [ 13.827724] </IRQ>
> | [ 13.827724] asm_sysvec_call_function_single+0x12/0x20
> | [ 13.827728] RIP: 0010:lock_release+0x178/0x460
> | ...
> | [ 13.827741] up_write+0x2f/0x1c0
> | [ 13.827743] anon_vma_clone+0x158/0x1f0
> | [ 13.827749] anon_vma_fork+0x33/0x180
> | [ 13.827751] dup_mm+0x45b/0x5f0
> | [ 13.827755] copy_process+0x1e5a/0x2050
> | [ 13.827758] kernel_clone+0x9b/0x3f0
> | [ 13.827760] ? vfs_statx+0x74/0x130
> | [ 13.827766] __do_sys_clone+0x60/0x80
> | [ 13.827769] do_syscall_64+0x3b/0x90
> | [ 13.827771] entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> The problem is rather coming from rt camp where splinlocks
> become sleepable thus can't be used in irq context (and for our kernel
> it requires the CONFIG_PROVE_RAW_LOCK_NESTING to be set), thus since
> we know that we're operating in irq context lets use raw spinlocks
> instead.
>
> https://jira.sw.ru/browse/PSBM-134761
>
> CC: Kirill Tkhai <ktk...@virtuozzo.com>
> Signed-off-by: Cyrill Gorcunov <gorcu...@gmail.com>
Reviewed-by: Kirill Tkhai <ktk...@virtuozzo.com>
> ---
> arch/x86/kernel/cpu/proc.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> --- vzkernel.orig/arch/x86/kernel/cpu/proc.c
> +++ vzkernel/arch/x86/kernel/cpu/proc.c
> @@ -69,7 +69,7 @@ struct cpu_flags {
> };
>
> static DEFINE_PER_CPU(struct cpu_flags, cpu_flags);
> -static DEFINE_SPINLOCK(cpu_flags_lock);
> +static DEFINE_RAW_SPINLOCK(cpu_flags_lock);
>
> static void init_cpu_flags(void *dummy)
> {
> @@ -107,9 +107,9 @@ static void init_cpu_flags(void *dummy)
> flags.val[10] &= eax;
> }
>
> - spin_lock(&cpu_flags_lock);
> + raw_spin_lock(&cpu_flags_lock);
> memcpy(&per_cpu(cpu_flags, cpu), &flags, sizeof(flags));
> - spin_unlock(&cpu_flags_lock);
> + raw_spin_unlock(&cpu_flags_lock);
> }
>
> static int show_cpuinfo(struct seq_file *m, void *v)
> @@ -158,9 +158,9 @@ static int show_cpuinfo(struct seq_file
> show_cpuinfo_misc(m, c);
>
> if (!is_super) {
> - spin_lock_irq(&cpu_flags_lock);
> + raw_spin_lock_irq(&cpu_flags_lock);
> memcpy(&ve_flags, &per_cpu(cpu_flags, cpu), sizeof(ve_flags));
> - spin_unlock_irq(&cpu_flags_lock);
> + raw_spin_unlock_irq(&cpu_flags_lock);
> }
>
>
>
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