Re: [PATCH V2 1/1] perf: event preserve and create across cpu hotplug
From: Mukesh Ojha
Date: Tue Jun 04 2019 - 10:13:38 EST
On 6/3/2019 11:23 PM, Jiri Olsa wrote:
On Fri, May 31, 2019 at 07:09:16PM +0530, Mukesh Ojha wrote:
Perf framework doesn't allow preserving CPU events across
CPU hotplugs. The events are scheduled out as and when the
CPU walks offline. Moreover, the framework also doesn't
allow the clients to create events on an offline CPU. As
a result, the clients have to keep on monitoring the CPU
state until it comes back online.
Therefore, introducing the perf framework to support creation
and preserving of (CPU) events for offline CPUs. Through
this, the CPU's online state would be transparent to the
client and it not have to worry about monitoring the CPU's
state. Success would be returned to the client even while
creating the event on an offline CPU. If during the lifetime
of the event the CPU walks offline, the event would be
preserved and would continue to count as soon as (and if) the
CPU comes back online.
Co-authored-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxxxxxx>
Signed-off-by: Mukesh Ojha <mojha@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
---
Change in V2:
As per long back discussion happened at
https://lkml.org/lkml/2018/2/15/1324
Peter.Z. has suggested to do thing in different way and shared
patch as well. This patch fixes the issue seen while trying
to achieve the purpose.
Fixed issue on top of Peter's patch:
===================================
1. Added a NULL check on task to avoid crash in __perf_install_in_context.
2. while trying to add event to context when cpu is offline.
Inside add_event_to_ctx() to make consistent state machine while hotplug.
-event->state += PERF_EVENT_STATE_HOTPLUG_OFFSET;
+event->state = PERF_EVENT_STATE_HOTPLUG_OFFSET;
3. In event_function_call(), added a label 'remove_event_from_ctx' to
delete events from context list while cpu is offline.
include/linux/perf_event.h | 1 +
kernel/events/core.c | 119 ++++++++++++++++++++++++++++-----------------
2 files changed, 76 insertions(+), 44 deletions(-)
hi,
I got crash on running "perf stat -a" and switching off
one cpu in another terminal via:
"echo 0 > /sys/devices/system/cpu/cpu2/online"
Thanks Jiri for the testing it.
jirka
---
ibm-x3650m4-01 login: [ 554.951780] smpboot: CPU 2 is now offline
[ 554.958301] BUG: kernel NULL pointer dereference, address: 0000000000000168
[ 554.966070] #PF: supervisor read access in kernel mode
[ 554.971802] #PF: error_code(0x0000) - not-present page
[ 554.977532] PGD 0 P4D 0
[ 554.980356] Oops: 0000 [#1] SMP PTI
[ 554.984256] CPU: 9 PID: 4782 Comm: bash Tainted: G W 5.2.0-rc1+ #3
[ 554.992605] Hardware name: IBM System x3650 M4 : -[7915E2G]-/00Y7683, BIOS -[VVE124AUS-1.30]- 11/21/2012
[ 555.003190] RIP: 0010:__perf_remove_from_context+0xcd/0x130
[ 555.009407] Code: 8b 3d 97 51 5f 60 e8 b2 4d ee ff 48 8b 95 b8 00 00 00 48 01 c2 48 2b 95 c0 00 00 00 48 89 85 c0 00 00 00 48 89 95 b8 00 00 00 <49> 8b 9c 24 68 01 00 00 48 85 db 0f 84 43 ff ff ff 65 8b 3d 5b 51
[ 555.030361] RSP: 0018:ffffaea78542fcb8 EFLAGS: 00010002
[ 555.036190] RAX: 0000008136178cad RBX: ffffa0c0f78b0008 RCX: 000000000000001f
[ 555.044151] RDX: 00000080bf70f331 RSI: 0000000040000219 RDI: fffc405d97b9b8a9
[ 555.052112] RBP: ffffa0c0f78b0000 R08: 0000000000000002 R09: 0000000000029500
[ 555.060074] R10: 00078047268106e0 R11: 0000000000000001 R12: 0000000000000000
[ 555.068037] R13: ffffa0bf86a5c000 R14: 0000000000000001 R15: 0000000000000001
[ 555.076000] FS: 00007f0ace1c9740(0000) GS:ffffa0c2f78c0000(0000) knlGS:0000000000000000
[ 555.085029] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 555.091438] CR2: 0000000000000168 CR3: 000000046c908001 CR4: 00000000000606e0
[ 555.099401] Call Trace:
[ 555.102133] ? perf_event_read_event+0x110/0x110
[ 555.107286] ? list_del_event+0x140/0x140
[ 555.111757] event_function_call+0x113/0x130
[ 555.116521] ? list_del_event+0x140/0x140
[ 555.120994] ? perf_event_read_event+0x110/0x110
[ 555.126144] perf_remove_from_context+0x20/0x70
[ 555.131200] perf_event_release_kernel+0x79/0x330
[ 555.136451] hardlockup_detector_perf_cleanup+0x33/0x8d
Looks like the support for arm64 is missing for
hardlockup_detector_perf_cleanup()
(HAVE_HARDLOCKUP_DETECTOR_PERF/HAVE_PERF_EVENTS_NMI),
i.e why it has passed for me.
Wondering what could have caused this,
lockup_detector_offline_cpu
Âwatchdog_disable
ÂÂ watchdog_nmi_disable
ÂÂÂÂ perf_event_disable(event);
Above path might have disabled the event, perf_remove_from_context this
might try to remove event from the context list.
My change only effects when event is destroyed while the offline cpu .
will look more into it .
Thanks,
Mukesh
[ 555.142282] lockup_detector_cleanup+0x16/0x30
[ 555.147241] _cpu_down+0xf3/0x1c0
[ 555.150941] do_cpu_down+0x2c/0x50
[ 555.154737] device_offline+0x81/0xb0
[ 555.158822] online_store+0x4a/0x90
[ 555.162714] kernfs_fop_write+0x116/0x190
[ 555.167188] vfs_write+0xa5/0x1a0
[ 555.170885] ksys_write+0x59/0xd0
[ 555.174583] do_syscall_64+0x55/0x1c0
[ 555.178670] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 555.184306] RIP: 0033:0x7f0acd8b1c58
[ 555.188301] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 c5 5a 2d 00 8b 00 85 c0 75 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 d4 55
[ 555.209261] RSP: 002b:00007ffe3883af68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 555.217709] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f0acd8b1c58
[ 555.225669] RDX: 0000000000000002 RSI: 000055ce3c955780 RDI: 0000000000000001
[ 555.233632] RBP: 000055ce3c955780 R08: 000000000000000a R09: 00007f0acd9433c0
[ 555.241594] R10: 000000000000000a R11: 0000000000000246 R12: 00007f0acdb83780
[ 555.249557] R13: 0000000000000002 R14: 00007f0acdb7e740 R15: 0000000000000002
[ 555.257521] Modules linked in: xt_MASQUERADE nf_nat xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ipt_REJECT nf_reject_ipv4 nft_counter nft_compat tun bridge stp llc nf_tables nfnetlink sunrpc intel_rapl sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm ipmi_ssif irqbypass crct10dif_pclmul crc32_pclmul ipmi_si ghash_clmulni_intel cdc_ether usbnet intel_cstate mii intel_uncore ipmi_devintf iTCO_wdt iTCO_vendor_support ipmi_msghandler sg wmi intel_rapl_perf ioatdma i2c_i801 pcspkr lpc_ich xfs libcrc32c sr_mod cdrom sd_mod mgag200 drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm ahci libahci igb crc32c_intel dca drm libata i2c_algo_bit megaraid_sas dm_mirror dm_region_hash dm_log dm_mod
[ 555.329511] CR2: 0000000000000168
[ 555.333218] ---[ end trace f871a38c5e6d1393 ]---
[ 555.338371] RIP: 0010:__perf_remove_from_context+0xcd/0x130
[ 555.344588] Code: 8b 3d 97 51 5f 60 e8 b2 4d ee ff 48 8b 95 b8 00 00 00 48 01 c2 48 2b 95 c0 00 00 00 48 89 85 c0 00 00 00 48 89 95 b8 00 00 00 <49> 8b 9c 24 68 01 00 00 48 85 db 0f 84 43 ff ff ff 65 8b 3d 5b 51
[ 555.365543] RSP: 0018:ffffaea78542fcb8 EFLAGS: 00010002
[ 555.371372] RAX: 0000008136178cad RBX: ffffa0c0f78b0008 RCX: 000000000000001f
[ 555.379334] RDX: 00000080bf70f331 RSI: 0000000040000219 RDI: fffc405d97b9b8a9
[ 555.387294] RBP: ffffa0c0f78b0000 R08: 0000000000000002 R09: 0000000000029500
[ 555.395264] R10: 00078047268106e0 R11: 0000000000000001 R12: 0000000000000000
[ 555.403228] R13: ffffa0bf86a5c000 R14: 0000000000000001 R15: 0000000000000001
[ 555.411189] FS: 00007f0ace1c9740(0000) GS:ffffa0c2f78c0000(0000) knlGS:0000000000000000
[ 555.420219] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 555.426630] CR2: 0000000000000168 CR3: 000000046c908001 CR4: 00000000000606e0
[ 555.434593] Kernel panic - not syncing: Fatal exception
[ 555.471650] Kernel Offset: 0x1e800000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[ 555.483688] ---[ end Kernel panic - not syncing: Fatal exception ]---