linux-kernel - [PATCH v2] MIPS: PCI: Fix smp_processor

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Date:   Tue, 25 Jul 2017 10:39:12 +0100
From:   Matt Redfearn <matt.redfearn@...tec.com>
To:     Ralf Baechle A <ralf@...ux-mips.org>
CC:     <linux-mips@...ux-mips.org>,
        Matt Redfearn <matt.redfearn@...tec.com>,
        "Maciej W. Rozycki" <macro@...tec.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        <linux-kernel@...r.kernel.org>,
        James Hogan <james.hogan@...tec.com>,
        Paul Burton <paul.burton@...tec.com>
Subject: [PATCH v2] MIPS: PCI: Fix smp_processor_id() in preemptible

Commit 1c3c5eab1715 ("sched/core: Enable might_sleep() and
smp_processor_id() checks early") enables checks for might_sleep() and
smp_processor_id() being used in preemptible code earlier in the boot
than before. This results in a new BUG from
pcibios_set_cache_line_size().

BUG: using smp_processor_id() in preemptible [00000000] code:
swapper/0/1
caller is pcibios_set_cache_line_size+0x10/0x70
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.13.0-rc1-00007-g3ce3e4ba4275 #615
Stack : 0000000000000000 ffffffff81189694 0000000000000000 ffffffff81822318
        000000000000004e 0000000000000001 800000000e20bd08 20c49ba5e3540000
        0000000000000000 0000000000000000 ffffffff818d0000 0000000000000000
        0000000000000000 ffffffff81189328 ffffffff818ce692 0000000000000000
        0000000000000000 ffffffff81189bc8 ffffffff818d0000 0000000000000000
        ffffffff81828907 ffffffff81769970 800000020ec78d80 ffffffff818c7b48
        0000000000000001 0000000000000001 ffffffff818652b0 ffffffff81896268
        ffffffff818c0000 800000020ec7fb40 800000020ec7fc58 ffffffff81684cac
        0000000000000000 ffffffff8118ab50 0000000000000030 ffffffff81769970
        0000000000000001 ffffffff81122a58 0000000000000000 0000000000000000
        ...
Call Trace:
[<ffffffff81122a58>] show_stack+0x90/0xb0
[<ffffffff81684cac>] dump_stack+0xac/0xf0
[<ffffffff813f7050>] check_preemption_disabled+0x120/0x128
[<ffffffff818855e8>] pcibios_set_cache_line_size+0x10/0x70
[<ffffffff81100578>] do_one_initcall+0x48/0x140
[<ffffffff81865dc4>] kernel_init_freeable+0x194/0x24c
[<ffffffff8169c534>] kernel_init+0x14/0x118
[<ffffffff8111ca84>] ret_from_kernel_thread+0x14/0x1c

Fix this by using the cpu_*cache_line_size() macros instead. These
macros are the "proper" way to determine the CPU cache sizes.
Since no cpu_tcache_line_size exists yet, add it.

Fixes: 1c3c5eab1715 ("sched/core: Enable might_sleep() and smp_processor_id() checks early")
Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
Suggested-by: James Hogan <james.hogan@...tec.com>
Reviewed-by: James Hogan <james.hogan@...tec.com>
---

Changes in v2:
Switch to using cpu_*cache_line_size() macros

In heteregenerous systems the more correct fix for this would be to
iterate over CPUs checking each ones cache hierarchy. However, as no
such systems currently exist that seems wasteful.

---
 arch/mips/include/asm/cpu-features.h | 3 +++
 arch/mips/pci/pci.c                  | 7 +++----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index 8baa9033b181..721b698bfe3c 100644
--- a/arch/mips/include/asm/cpu-features.h
+++ b/arch/mips/include/asm/cpu-features.h
@@ -428,6 +428,9 @@
 #ifndef cpu_scache_line_size
 #define cpu_scache_line_size()	cpu_data[0].scache.linesz
 #endif
+#ifndef cpu_tcache_line_size
+#define cpu_tcache_line_size()	cpu_data[0].tcache.linesz
+#endif
 
 #ifndef cpu_hwrena_impl_bits
 #define cpu_hwrena_impl_bits		0
diff --git a/arch/mips/pci/pci.c b/arch/mips/pci/pci.c
index bd67ac74fe2d..9632436d74d7 100644
--- a/arch/mips/pci/pci.c
+++ b/arch/mips/pci/pci.c
@@ -28,16 +28,15 @@ EXPORT_SYMBOL(PCIBIOS_MIN_MEM);
 
 static int __init pcibios_set_cache_line_size(void)
 {
-	struct cpuinfo_mips *c = &current_cpu_data;
 	unsigned int lsize;
 
 	/*
 	 * Set PCI cacheline size to that of the highest level in the
 	 * cache hierarchy.
 	 */
-	lsize = c->dcache.linesz;
-	lsize = c->scache.linesz ? : lsize;
-	lsize = c->tcache.linesz ? : lsize;
+	lsize = cpu_dcache_line_size();
+	lsize = cpu_scache_line_size() ? : lsize;
+	lsize = cpu_tcache_line_size() ? : lsize;
 
 	BUG_ON(!lsize);
 
-- 
2.7.4