linux-kernel - [RFC][WARNING] warning in uncore_pci

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Message-ID: <20160517145648.GA28658@krava>
Date:	Tue, 17 May 2016 16:56:48 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	x86@...nel.org, Ingo Molnar <mingo@...nel.org>
Subject: [RFC][WARNING] warning in uncore_pci_probe


hi,
I'm hitting following warning:

[    2.766466] WARNING: CPU: 0 PID: 1 at arch/x86/events/intel/uncore.c:894 uncore_pci_probe+0x2a8/0x2b0
[    2.776749] Modules linked in:
[    2.780166] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0tip+ #7
[    2.787060] Hardware name: Dell Inc. PowerEdge R520/08DM12, BIOS 2.1.2 01/20/2014
[    2.795409]  0000000000000286 00000000893ec9e0 ffff880624607bb0 ffffffff8134913c
[    2.803698]  0000000000000000 0000000000000000 ffff880624607bf0 ffffffff8108c761
[    2.811988]  0000037effffffff ffffffff81802d20 0000000000000000 ffff88062436e000
[    2.820275] Call Trace:
[    2.823006]  [<ffffffff8134913c>] dump_stack+0x63/0x87
[    2.828730]  [<ffffffff8108c761>] __warn+0xd1/0xf0
[    2.834074]  [<ffffffff8108c89d>] warn_slowpath_null+0x1d/0x20
[    2.840581]  [<ffffffff81015208>] uncore_pci_probe+0x2a8/0x2b0
[    2.847093]  [<ffffffff8138af25>] local_pci_probe+0x45/0xa0
[    2.853310]  [<ffffffff8135e749>] ? find_next_bit+0x19/0x20
[    2.859525]  [<ffffffff8138c3a6>] pci_device_probe+0x136/0x140
[    2.866034]  [<ffffffff81478be9>] driver_probe_device+0x239/0x460
[    2.872831]  [<ffffffff81478ed9>] __driver_attach+0xc9/0xf0
[    2.879046]  [<ffffffff81478e10>] ? driver_probe_device+0x460/0x460
[    2.886038]  [<ffffffff8147676c>] bus_for_each_dev+0x6c/0xc0
[    2.892350]  [<ffffffff8147845e>] driver_attach+0x1e/0x20
[    2.898373]  [<ffffffff81477ed0>] bus_add_driver+0x1d0/0x290
[    2.904686]  [<ffffffff81d85785>] ? uncore_cpu_setup+0x17/0x17
[    2.911195]  [<ffffffff81479980>] driver_register+0x60/0xe0
[    2.917412]  [<ffffffff8138a85c>] __pci_register_driver+0x4c/0x50
[    2.924210]  [<ffffffff81d859fc>] intel_uncore_init+0x277/0x2dd
[    2.930813]  [<ffffffff81d85785>] ? uncore_cpu_setup+0x17/0x17
[    2.937322]  [<ffffffff8100213d>] do_one_initcall+0xcd/0x1f0
[    2.943636]  [<ffffffff810ab933>] ? parse_args+0x293/0x480
[    2.949755]  [<ffffffff81d80360>] kernel_init_freeable+0x1a5/0x249
[    2.956650]  [<ffffffff81d7fa35>] ? set_debug_rodata+0x12/0x12
[    2.963161]  [<ffffffff816b5f0e>] kernel_init+0xe/0x110
[    2.968991]  [<ffffffff816c2c3f>] ret_from_fork+0x1f/0x40
[    2.975012]  [<ffffffff816b5f00>] ? rest_init+0x80/0x80


I'm booting with nr_cpus=1, which impact physical_to_logical_pkg
setup.. the map will not be initialized because the rest of cpus
is never initialized and set in cpu_present_mask

it seems to me we should remove the warning, because it's valid to
have only single cpu allowed

thanks,
jirka


---
diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 7012d18bb293..f921a1ed43f7 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -888,7 +888,7 @@ static int uncore_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id
 		return -ENODEV;
 
 	pkg = topology_phys_to_logical_pkg(phys_id);
-	if (WARN_ON_ONCE(pkg < 0))
+	if (pkg < 0)
 		return -EINVAL;
 
 	if (UNCORE_PCI_DEV_TYPE(id->driver_data) == UNCORE_EXTRA_PCI_DEV) {