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Date: Tue, 23 Mar 2021 16:56:27 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Like Xu <like.xu@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 RESEND 3/5] perf/x86/lbr: Move cpuc->lbr_xsave
allocation out of sleeping region
On 3/22/2021 2:06 AM, Like Xu wrote:
> If the kernel is compiled with the CONFIG_LOCKDEP option, the conditional
> might_sleep_if() deep in kmem_cache_alloc() will generate the following
> trace, and potentially cause a deadlock when another LBR event is added:
>
> [ 243.115549] BUG: sleeping function called from invalid context at include/linux/sched/mm.h:196
> [ 243.117576] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 839, name: perf
> [ 243.119326] INFO: lockdep is turned off.
> [ 243.120249] irq event stamp: 0
> [ 243.120967] hardirqs last enabled at (0): [<0000000000000000>] 0x0
> [ 243.122415] hardirqs last disabled at (0): [<ffffffff810d9bf5>] copy_process+0xa45/0x1dc0
> [ 243.124302] softirqs last enabled at (0): [<ffffffff810d9bf5>] copy_process+0xa45/0x1dc0
> [ 243.126255] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [ 243.128119] CPU: 0 PID: 839 Comm: perf Not tainted 5.11.0-rc4-guest+ #8
> [ 243.129654] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> [ 243.131520] Call Trace:
> [ 243.132112] dump_stack+0x8d/0xb5
> [ 243.132896] ___might_sleep.cold.106+0xb3/0xc3
> [ 243.133984] slab_pre_alloc_hook.constprop.85+0x96/0xd0
> [ 243.135208] ? intel_pmu_lbr_add+0x152/0x170
> [ 243.136207] kmem_cache_alloc+0x36/0x250
> [ 243.137126] intel_pmu_lbr_add+0x152/0x170
> [ 243.138088] x86_pmu_add+0x83/0xd0
> [ 243.138889] ? lock_acquire+0x158/0x350
> [ 243.139791] ? lock_acquire+0x158/0x350
> [ 243.140694] ? lock_acquire+0x158/0x350
> [ 243.141625] ? lock_acquired+0x1e3/0x360
> [ 243.142544] ? lock_release+0x1bf/0x340
> [ 243.143726] ? trace_hardirqs_on+0x1a/0xd0
> [ 243.144823] ? lock_acquired+0x1e3/0x360
> [ 243.145742] ? lock_release+0x1bf/0x340
> [ 243.147107] ? __slab_free+0x49/0x540
> [ 243.147966] ? trace_hardirqs_on+0x1a/0xd0
> [ 243.148924] event_sched_in.isra.129+0xf8/0x2a0
> [ 243.149989] merge_sched_in+0x261/0x3e0
> [ 243.150889] ? trace_hardirqs_on+0x1a/0xd0
> [ 243.151869] visit_groups_merge.constprop.135+0x130/0x4a0
> [ 243.153122] ? sched_clock_cpu+0xc/0xb0
> [ 243.154023] ctx_sched_in+0x101/0x210
> [ 243.154884] ctx_resched+0x6f/0xc0
> [ 243.155686] perf_event_exec+0x21e/0x2e0
> [ 243.156641] begin_new_exec+0x5e5/0xbd0
> [ 243.157540] load_elf_binary+0x6af/0x1770
> [ 243.158478] ? __kernel_read+0x19d/0x2b0
> [ 243.159977] ? lock_acquire+0x158/0x350
> [ 243.160876] ? __kernel_read+0x19d/0x2b0
> [ 243.161796] bprm_execve+0x3c8/0x840
> [ 243.162638] do_execveat_common.isra.38+0x1a5/0x1c0
> [ 243.163776] __x64_sys_execve+0x32/0x40
> [ 243.164676] do_syscall_64+0x33/0x40
> [ 243.165514] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 243.166746] RIP: 0033:0x7f6180a26feb
> [ 243.167590] Code: Unable to access opcode bytes at RIP 0x7f6180a26fc1.
> [ 243.169097] RSP: 002b:00007ffc6558ce18 EFLAGS: 00000202 ORIG_RAX: 000000000000003b
> [ 243.170844] RAX: ffffffffffffffda RBX: 00007ffc65592d30 RCX: 00007f6180a26feb
> [ 243.172514] RDX: 000055657f408dc0 RSI: 00007ffc65592410 RDI: 00007ffc65592d30
> [ 243.174162] RBP: 00007ffc6558ce80 R08: 00007ffc6558cde0 R09: 0000000000000000
> [ 243.176042] R10: 0000000000000008 R11: 0000000000000202 R12: 00007ffc65592410
> [ 243.177696] R13: 000055657f408dc0 R14: 0000000000000001 R15: 00007ffc65592410
>
> One of the solution is to use GFP_ATOMIC, but it will make the code less
> reliable under memory pressue. Let's move the memory allocation out of
> the sleeping region and put it into the x86_reserve_hardware().
>
> The disadvantage of this fix is that the cpuc->lbr_xsave memory
> will be allocated for each cpu like the legacy ds_buffer.
>
> Fixes: c085fb8774 ("perf/x86/intel/lbr: Support XSAVES for arch LBR read")
> Suggested-by: Kan Liang <kan.liang@...ux.intel.com>
> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
I observed the same issue when I did LBR test on an ADL machine. This
patch fixes the issue.
Tested-by: Kan Liang <kan.liang@...ux.intel.com>
Thanks,
Kan
> ---
> arch/x86/events/core.c | 8 +++++---
> arch/x86/events/intel/bts.c | 2 +-
> arch/x86/events/intel/lbr.c | 22 ++++++++++++++++------
> arch/x86/events/perf_event.h | 8 +++++++-
> 4 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> index 18df17129695..a4ce669cc78d 100644
> --- a/arch/x86/events/core.c
> +++ b/arch/x86/events/core.c
> @@ -373,7 +373,7 @@ set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event *event)
> return x86_pmu_extra_regs(val, event);
> }
>
> -int x86_reserve_hardware(void)
> +int x86_reserve_hardware(struct perf_event *event)
> {
> int err = 0;
>
> @@ -382,8 +382,10 @@ int x86_reserve_hardware(void)
> if (atomic_read(&pmc_refcount) == 0) {
> if (!reserve_pmc_hardware())
> err = -EBUSY;
> - else
> + else {
> reserve_ds_buffers();
> + reserve_lbr_buffers(event);
> + }
> }
> if (!err)
> atomic_inc(&pmc_refcount);
> @@ -634,7 +636,7 @@ static int __x86_pmu_event_init(struct perf_event *event)
> if (!x86_pmu_initialized())
> return -ENODEV;
>
> - err = x86_reserve_hardware();
> + err = x86_reserve_hardware(event);
> if (err)
> return err;
>
> diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
> index 731dd8d0dbb1..057bb2f761a9 100644
> --- a/arch/x86/events/intel/bts.c
> +++ b/arch/x86/events/intel/bts.c
> @@ -564,7 +564,7 @@ static int bts_event_init(struct perf_event *event)
> if (x86_add_exclusive(x86_lbr_exclusive_bts))
> return -EBUSY;
>
> - ret = x86_reserve_hardware();
> + ret = x86_reserve_hardware(event);
> if (ret) {
> x86_del_exclusive(x86_lbr_exclusive_bts);
> return ret;
> diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
> index 355ea70f1879..237876733e12 100644
> --- a/arch/x86/events/intel/lbr.c
> +++ b/arch/x86/events/intel/lbr.c
> @@ -658,7 +658,6 @@ static inline bool branch_user_callstack(unsigned br_sel)
>
> void intel_pmu_lbr_add(struct perf_event *event)
> {
> - struct kmem_cache *kmem_cache = event->pmu->task_ctx_cache;
> struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
>
> if (!x86_pmu.lbr_nr)
> @@ -696,11 +695,6 @@ void intel_pmu_lbr_add(struct perf_event *event)
> perf_sched_cb_inc(event->ctx->pmu);
> if (!cpuc->lbr_users++ && !event->total_time_running)
> intel_pmu_lbr_reset();
> -
> - if (static_cpu_has(X86_FEATURE_ARCH_LBR) &&
> - kmem_cache && !cpuc->lbr_xsave &&
> - (cpuc->lbr_users != cpuc->lbr_pebs_users))
> - cpuc->lbr_xsave = kmem_cache_alloc(kmem_cache, GFP_KERNEL);
> }
>
> void release_lbr_buffers(void)
> @@ -721,6 +715,22 @@ void release_lbr_buffers(void)
> }
> }
>
> +void reserve_lbr_buffers(struct perf_event *event)
> +{
> + struct kmem_cache *kmem_cache = x86_get_pmu()->task_ctx_cache;
> + struct cpu_hw_events *cpuc;
> + int cpu;
> +
> + if (!static_cpu_has(X86_FEATURE_ARCH_LBR))
> + return;
> +
> + for_each_possible_cpu(cpu) {
> + cpuc = per_cpu_ptr(&cpu_hw_events, cpu);
> + if (kmem_cache && !cpuc->lbr_xsave && !event->attr.precise_ip)
> + cpuc->lbr_xsave = kmem_cache_alloc(kmem_cache, GFP_KERNEL);
> + }
> +}
> +
> void intel_pmu_lbr_del(struct perf_event *event)
> {
> struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
> index 53b2b5fc23bc..2fe77d3a98d6 100644
> --- a/arch/x86/events/perf_event.h
> +++ b/arch/x86/events/perf_event.h
> @@ -968,7 +968,7 @@ int x86_add_exclusive(unsigned int what);
>
> void x86_del_exclusive(unsigned int what);
>
> -int x86_reserve_hardware(void);
> +int x86_reserve_hardware(struct perf_event *event);
>
> void x86_release_hardware(void);
>
> @@ -1135,6 +1135,8 @@ void reserve_ds_buffers(void);
>
> void release_lbr_buffers(void);
>
> +void reserve_lbr_buffers(struct perf_event *event);
> +
> extern struct event_constraint bts_constraint;
> extern struct event_constraint vlbr_constraint;
>
> @@ -1282,6 +1284,10 @@ static inline void release_lbr_buffers(void)
> {
> }
>
> +static inline void reserve_lbr_buffers(struct perf_event *event)
> +{
> +}
> +
> static inline int intel_pmu_init(void)
> {
> return 0;
>
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