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Corrected minor typos in intro lecture #14

Merged
merged 2 commits into from
Feb 27, 2018
Merged

Corrected minor typos in intro lecture #14

merged 2 commits into from
Feb 27, 2018

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tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Feb 27, 2018
Publish pull/14 (built from linux-kernel-labs/linux#14)
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dbaluta commented Feb 27, 2018

Looks good to me. Tavi please merge.

@tavip tavip merged commit d49ac51 into linux-kernel-labs:master Feb 27, 2018
dbaluta pushed a commit to dbaluta/linux that referenced this pull request Nov 7, 2019
@rgushchin @torvalds
mm: memcg/slab: fix panic in __free_slab() caused by premature memcg …
b749ecf 
…pointer release

Karsten reported the following panic in __free_slab() happening on a s390x
machine:

  Unable to handle kernel pointer dereference in virtual kernel address space
  Failing address: 0000000000000000 TEID: 0000000000000483
  Fault in home space mode while using kernel ASCE.
  AS:00000000017d4007 R3:000000007fbd0007 S:000000007fbff000 P:000000000000003d
  Oops: 0004 ilc:3 Ý#1¨ PREEMPT SMP
  Modules linked in: tcp_diag inet_diag xt_tcpudp ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_at nf_nat
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.3.0-05872-g6133e3e4bada-dirty linux-kernel-labs#14
  Hardware name: IBM 2964 NC9 702 (z/VM 6.4.0)
  Krnl PSW : 0704d00180000000 00000000003cadb6 (__free_slab+0x686/0x6b0)
             R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
  Krnl GPRS: 00000000f3a32928 0000000000000000 000000007fbf5d00 000000000117c4b8
             0000000000000000 000000009e3291c1 0000000000000000 0000000000000000
             0000000000000003 0000000000000008 000000002b478b00 000003d080a97600
             0000000000000003 0000000000000008 000000002b478b00 000003d080a97600
             000000000117ba00 000003e000057db0 00000000003cabcc 000003e000057c78
  Krnl Code: 00000000003cada6: e310a1400004        lg      %r1,320(%r10)
             00000000003cadac: c0e50046c286        brasl   %r14,ca32b8
            #00000000003cadb2: a7f4fe36            brc     15,3caa1e
            >00000000003cadb6: e32060800024        stg     %r2,128(%r6)
             00000000003cadbc: a7f4fd9e            brc     15,3ca8f8
             00000000003cadc0: c0e50046790c        brasl   %r14,c99fd8
             00000000003cadc6: a7f4fe2c            brc     15,3caa
             00000000003cadc6: a7f4fe2c            brc     15,3caa1e
             00000000003cadca: ecb1ffff00d9        aghik   %r11,%r1,-1
  Call Trace:
  (<00000000003cabcc> __free_slab+0x49c/0x6b0)
   <00000000001f5886> rcu_core+0x5a6/0x7e0
   <0000000000ca2dea> __do_softirq+0xf2/0x5c0
   <0000000000152644> irq_exit+0x104/0x130
   <000000000010d222> do_IRQ+0x9a/0xf0
   <0000000000ca2344> ext_int_handler+0x130/0x134
   <0000000000103648> enabled_wait+0x58/0x128
  (<0000000000103634> enabled_wait+0x44/0x128)
   <0000000000103b00> arch_cpu_idle+0x40/0x58
   <0000000000ca0544> default_idle_call+0x3c/0x68
   <000000000018eaa4> do_idle+0xec/0x1c0
   <000000000018ee0e> cpu_startup_entry+0x36/0x40
   <000000000122df34> arch_call_rest_init+0x5c/0x88
   <0000000000000000> 0x0
  INFO: lockdep is turned off.
  Last Breaking-Event-Address:
   <00000000003ca8f4> __free_slab+0x1c4/0x6b0
  Kernel panic - not syncing: Fatal exception in interrupt

The kernel panics on an attempt to dereference the NULL memcg pointer.
When shutdown_cache() is called from the kmem_cache_destroy() context, a
memcg kmem_cache might have empty slab pages in a partial list, which are
still charged to the memory cgroup.

These pages are released by free_partial() at the beginning of
shutdown_cache(): either directly or by scheduling a RCU-delayed work
(if the kmem_cache has the SLAB_TYPESAFE_BY_RCU flag).  The latter case
is when the reported panic can happen: memcg_unlink_cache() is called
immediately after shrinking partial lists, without waiting for scheduled
RCU works.  It sets the kmem_cache->memcg_params.memcg pointer to NULL,
and the following attempt to dereference it by __free_slab() from the
RCU work context causes the panic.

To fix the issue, let's postpone the release of the memcg pointer to
destroy_memcg_params().  It's called from a separate work context by
slab_caches_to_rcu_destroy_workfn(), which contains a full RCU barrier.
This guarantees that all scheduled page release RCU works will complete
before the memcg pointer will be zeroed.

Big thanks for Karsten for the perfect report containing all necessary
information, his help with the analysis of the problem and testing of the
fix.

Link: http://lkml.kernel.org/r/20191010160549.1584316-1-guro@fb.com
Fixes: fb2f2b0 ("mm: memcg/slab: reparent memcg kmem_caches on cgroup removal")
Signed-off-by: Roman Gushchin <guro@fb.com>
Reported-by: Karsten Graul <kgraul@linux.ibm.com>
Tested-by: Karsten Graul <kgraul@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Karsten Graul <kgraul@linux.ibm.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
dbaluta pushed a commit to dbaluta/linux that referenced this pull request Nov 15, 2019
@Lyude
igb/igc: Don't warn on fatal read failures when the device is removed
94bc1e5 
Fatal read errors are worth warning about, unless of course the device
was just unplugged from the machine - something that's a rather normal
occurrence when the igb/igc adapter is located on a Thunderbolt dock. So,
let's only WARN() if there's a fatal read error while the device is
still present.

This fixes the following WARN splat that's been appearing whenever I
unplug my Caldigit TS3 Thunderbolt dock from my laptop:

  igb 0000:09:00.0 enp9s0: PCIe link lost
  ------------[ cut here ]------------
  igb: Failed to read reg 0x18!
  WARNING: CPU: 7 PID: 516 at
  drivers/net/ethernet/intel/igb/igb_main.c:756 igb_rd32+0x57/0x6a [igb]
  Modules linked in: igb dca thunderbolt fuse vfat fat elan_i2c mei_wdt
  mei_hdcp i915 wmi_bmof intel_wmi_thunderbolt iTCO_wdt
  iTCO_vendor_support x86_pkg_temp_thermal intel_powerclamp joydev
  coretemp crct10dif_pclmul crc32_pclmul i2c_algo_bit ghash_clmulni_intel
  intel_cstate drm_kms_helper intel_uncore syscopyarea sysfillrect
  sysimgblt fb_sys_fops intel_rapl_perf intel_xhci_usb_role_switch mei_me
  drm roles idma64 i2c_i801 ucsi_acpi typec_ucsi mei intel_lpss_pci
  processor_thermal_device typec intel_pch_thermal intel_soc_dts_iosf
  intel_lpss int3403_thermal thinkpad_acpi wmi int340x_thermal_zone
  ledtrig_audio int3400_thermal acpi_thermal_rel acpi_pad video
  pcc_cpufreq ip_tables serio_raw nvme nvme_core crc32c_intel uas
  usb_storage e1000e i2c_dev
  CPU: 7 PID: 516 Comm: kworker/u16:3 Not tainted 5.2.0-rc1Lyude-Test+ linux-kernel-labs#14
  Hardware name: LENOVO 20L8S2N800/20L8S2N800, BIOS N22ET35W (1.12 ) 04/09/2018
  Workqueue: kacpi_hotplug acpi_hotplug_work_fn
  RIP: 0010:igb_rd32+0x57/0x6a [igb]
  Code: 87 b8 fc ff ff 48 c7 47 08 00 00 00 00 48 c7 c6 33 42 9b c0 4c 89
  c7 e8 47 45 cd dc 89 ee 48 c7 c7 43 42 9b c0 e8 c1 94 71 dc <0f> 0b eb
  08 8b 00 ff c0 75 b0 eb c8 44 89 e0 5d 41 5c c3 0f 1f 44
  RSP: 0018:ffffba5801cf7c48 EFLAGS: 00010286
  RAX: 0000000000000000 RBX: ffff9e7956608840 RCX: 0000000000000007
  RDX: 0000000000000000 RSI: ffffba5801cf7b24 RDI: ffff9e795e3d6a00
  RBP: 0000000000000018 R08: 000000009dec4a01 R09: ffffffff9e61018f
  R10: 0000000000000000 R11: ffffba5801cf7ae5 R12: 00000000ffffffff
  R13: ffff9e7956608840 R14: ffff9e795a6f10b0 R15: 0000000000000000
  FS:  0000000000000000(0000) GS:ffff9e795e3c0000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000564317bc4088 CR3: 000000010e00a006 CR4: 00000000003606e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   igb_release_hw_control+0x1a/0x30 [igb]
   igb_remove+0xc5/0x14b [igb]
   pci_device_remove+0x3b/0x93
   device_release_driver_internal+0xd7/0x17e
   pci_stop_bus_device+0x36/0x75
   pci_stop_bus_device+0x66/0x75
   pci_stop_bus_device+0x66/0x75
   pci_stop_and_remove_bus_device+0xf/0x19
   trim_stale_devices+0xc5/0x13a
   ? __pm_runtime_resume+0x6e/0x7b
   trim_stale_devices+0x103/0x13a
   ? __pm_runtime_resume+0x6e/0x7b
   trim_stale_devices+0x103/0x13a
   acpiphp_check_bridge+0xd8/0xf5
   acpiphp_hotplug_notify+0xf7/0x14b
   ? acpiphp_check_bridge+0xf5/0xf5
   acpi_device_hotplug+0x357/0x3b5
   acpi_hotplug_work_fn+0x1a/0x23
   process_one_work+0x1a7/0x296
   worker_thread+0x1a8/0x24c
   ? process_scheduled_works+0x2c/0x2c
   kthread+0xe9/0xee
   ? kthread_destroy_worker+0x41/0x41
   ret_from_fork+0x35/0x40
  ---[ end trace 252bf10352c63d22 ]---

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 47e1669 ("igb/igc: warn when fatal read failure happens")
Acked-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Acked-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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@alex-mocanu @dbaluta @tavip