Re: [PATCH] IB/mad: Use ID allocator routines to allocate agent number

From: Leon Romanovsky
Date: Tue May 29 2018 - 05:55:00 EST


On Tue, May 29, 2018 at 11:54:59AM +0300, Leon Romanovsky wrote:
> On Tue, May 29, 2018 at 09:38:08AM +0200, Hans Westgaard Ry wrote:
> > The agent TID is a 64 bit value split in two dwords. The least
> > significant dword is the TID running counter. The most significant
> > dword is the agent number. In the CX-3 shared port model, the mlx4
> > driver uses the most significant byte of the agent number to store the
> > slave number, making agent numbers greater and equal to 2^24 (3 bytes)
> > unusable. The current codebase uses a variable which is incremented
> > atomically for each new agent number giving too large agent numbers
> > over time. The IDA set of functions are used instead of the simple
> > counter approach. This allows re-use of agent numbers. A sysctl
> > variable is also introduced, to control the max agent number.
>
> Why don't you simply limit this number per-driver? By default, any
> variable is allowed and mlx4_ib will set something else.
>
> What is the advantage of having sysctl?

Anyway, it doesn't pass smoke test.

[ 126.428407] RPC: Unregistered rdma transport module.
[ 126.428513] RPC: Unregistered rdma backchannel transport module.
[ 194.664081] IPv6: ADDRCONF(NETDEV_UP): ib0: link is not ready
[ 209.068702] BUG: unable to handle kernel NULL pointer dereference at 0000000000000070
[ 209.068858] PGD 80000000341cf067 P4D 80000000341cf067 PUD 34188067 PMD 0
[ 209.068941] Oops: 0002 [#1] SMP PTI
[ 209.069006] Modules linked in: netconsole nfsv3 nfs fscache
mlx4_ib(-) mlx4_en mlx4_core devlink ib_ipoib rdma_ucm ib_ucm ib_uverbs
ib_umad rdma_cm ib_cm iw_cm ib_core dm_mirror dm_region_hash dm_log
dm_mod nfsd pcspkr i2c_piix4 auth_rpcgss nfs_acl lockd grace sunrpc
ip_tables ata_generic cirrus drm_kms_helper pata_acpi syscopyarea
sysfillrect sysimgblt fb_sys_fops ttm drm e1000 virtio_console i2c_core
serio_raw ata_piix floppy [last unloaded: mlxfw]
[ 209.069312] CPU: 4 PID: 11048 Comm: modprobe Not tainted 4.17.0-rc7-2018-05-29_11-04-56_Hans_Westgaard_Ry__hans_westga #1
[ 209.069413] Hardware name: Red Hat KVM, BIOS Bochs 01/01/2011
[ 209.069486] RIP: 0010:_raw_spin_lock_irqsave+0x1e/0x40
[ 209.069536] RSP: 0018:ffffc90000b4fd70 EFLAGS: 00010046
[ 209.069591] RAX: 0000000000000000 RBX: 0000000000000246 RCX: ffffea0004d7ed00
[ 209.069653] RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000070
[ 209.069717] RBP: 0000000000000000 R08: ffff88013446fc00 R09: 000000018010000f
[ 209.069778] R10: 0000000000000001 R11: ffff88013446fc00 R12: 0000000000000070
[ 209.069849] R13: 0000000000000202 R14: 0000000000000000 R15: 0000000000000000
[ 209.069915] FS: 00007fc34caf7740(0000) GS:ffff88013fd00000(0000) knlGS:0000000000000000
[ 209.069987] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 209.070043] CR2: 0000000000000070 CR3: 000000008853e000 CR4: 00000000000006e0
[ 209.070128] Call Trace:
[ 209.070189] ib_unregister_mad_agent+0x2d/0x540 [ib_core]
[ 209.070260] ? __slab_free+0x9a/0x2d0
[ 209.070332] ib_agent_port_close+0xad/0xf0 [ib_core]
[ 209.070396] ib_mad_remove_device+0x59/0xb0 [ib_core]
[ 209.070466] ib_unregister_device+0xd4/0x180 [ib_core]
[ 209.070537] mlx4_ib_remove+0x67/0x1f0 [mlx4_ib]
[ 209.070594] mlx4_remove_device+0x93/0xa0 [mlx4_core]
[ 209.070648] mlx4_unregister_interface+0x37/0x90 [mlx4_core]
[ 209.070705] mlx4_ib_cleanup+0xc/0x4db [mlx4_ib]
[ 209.072113] __x64_sys_delete_module+0x15b/0x260
[ 209.073567] ? exit_to_usermode_loop+0x7f/0x95
[ 209.074945] do_syscall_64+0x48/0x100
[ 209.076448] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 209.077799] RIP: 0033:0x7fc34bfe36b7
[ 209.079122] RSP: 002b:00007ffc8ffa98b8 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
[ 209.080500] RAX: ffffffffffffffda RBX: 00000000013455c0 RCX: 00007fc34bfe36b7
[ 209.081875] RDX: 0000000000000000 RSI: 0000000000000800 RDI: 0000000001345628
[ 209.083265] RBP: 0000000000000000 R08: 00007fc34c2a8060 R09: 00007fc34c053a40
[ 209.084655] R10: 00007ffc8ffa9640 R11: 0000000000000206 R12: 0000000000000000
[ 209.086028] R13: 0000000000000001 R14: 0000000001345628 R15: 0000000000000000
[ 209.087416] Code: 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00
00 53 9c 58 0f 1f 44 00 00 48 89 c3 fa 66 0f 1f 44 00 00 31 c0 ba 01 00
00 00 <f0> 0f b1 17 85 c0 75 05 48 89 d8 5b c3 89 c6 e8 1e c9 81 ff eb
[ 209.090262] RIP: _raw_spin_lock_irqsave+0x1e/0x40 RSP: ffffc90000b4fd70
[ 209.091720] CR2: 0000000000000070
[ 209.093137] ---[ end trace 7b8a6faa27868861 ]---
[ 209.094546] Kernel panic - not syncing: Fatal exception
[ 209.096910] Kernel Offset: disabled
[ 209.098291] ---[ end Kernel panic - not syncing: Fatal exception ]---

Thanks

>
> Thanks


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