[PATCH] iommu: Disable preemption around use of this_cpu_ptr()
From: Chris Wilson
Date: Tue May 31 2016 - 12:34:47 EST
Between acquiring the this_cpu_ptr() and using it, ideally we don't want
to be preempted and work on another CPU's private data. If we disable
preemption around this_cpu_ptr, we do not need the CPU local spinlock -
so long as take care that no other CPU is running that code as do perform
the cross-CPU cache flushing and teardown.
[ 167.997877] BUG: using smp_processor_id() in preemptible [00000000] code: usb-storage/216
[ 167.997940] caller is debug_smp_processor_id+0x17/0x20
[ 167.997945] CPU: 7 PID: 216 Comm: usb-storage Tainted: G U 4.7.0-rc1-gfxbench-RO_Patchwork_1057+ #1
[ 167.997948] Hardware name: Hewlett-Packard HP Pro 3500 Series/2ABF, BIOS 8.11 10/24/2012
[ 167.997951] 0000000000000000 ffff880118b7f9c8 ffffffff8140dca5 0000000000000007
[ 167.997958] ffffffff81a3a7e9 ffff880118b7f9f8 ffffffff8142a927 0000000000000000
[ 167.997965] ffff8800d499ed58 0000000000000001 00000000000fffff ffff880118b7fa08
[ 167.997971] Call Trace:
[ 167.997977] [<ffffffff8140dca5>] dump_stack+0x67/0x92
[ 167.997981] [<ffffffff8142a927>] check_preemption_disabled+0xd7/0xe0
[ 167.997985] [<ffffffff8142a947>] debug_smp_processor_id+0x17/0x20
[ 167.997990] [<ffffffff81507e17>] alloc_iova_fast+0xb7/0x210
[ 167.997994] [<ffffffff8150c55f>] intel_alloc_iova+0x7f/0xd0
[ 167.997998] [<ffffffff8151021d>] intel_map_sg+0xbd/0x240
[ 167.998002] [<ffffffff810e5efd>] ? debug_lockdep_rcu_enabled+0x1d/0x20
[ 167.998009] [<ffffffff81596059>] usb_hcd_map_urb_for_dma+0x4b9/0x5a0
[ 167.998013] [<ffffffff81596d19>] usb_hcd_submit_urb+0xe9/0xaa0
[ 167.998017] [<ffffffff810cff2f>] ? mark_held_locks+0x6f/0xa0
[ 167.998022] [<ffffffff810d525c>] ? __raw_spin_lock_init+0x1c/0x50
[ 167.998025] [<ffffffff810e5efd>] ? debug_lockdep_rcu_enabled+0x1d/0x20
[ 167.998028] [<ffffffff815988f3>] usb_submit_urb+0x3f3/0x5a0
[ 167.998032] [<ffffffff810d0082>] ? trace_hardirqs_on_caller+0x122/0x1b0
[ 167.998035] [<ffffffff81599ae7>] usb_sg_wait+0x67/0x150
[ 167.998039] [<ffffffff815dc202>] usb_stor_bulk_transfer_sglist.part.3+0x82/0xd0
[ 167.998042] [<ffffffff815dc29c>] usb_stor_bulk_srb+0x4c/0x60
[ 167.998045] [<ffffffff815dc42e>] usb_stor_Bulk_transport+0x17e/0x420
[ 167.998049] [<ffffffff815dcf32>] usb_stor_invoke_transport+0x242/0x540
[ 167.998052] [<ffffffff810e5efd>] ? debug_lockdep_rcu_enabled+0x1d/0x20
[ 167.998058] [<ffffffff815dba19>] usb_stor_transparent_scsi_command+0x9/0x10
[ 167.998061] [<ffffffff815de518>] usb_stor_control_thread+0x158/0x260
[ 167.998064] [<ffffffff815de3c0>] ? fill_inquiry_response+0x20/0x20
[ 167.998067] [<ffffffff815de3c0>] ? fill_inquiry_response+0x20/0x20
[ 167.998071] [<ffffffff8109ddfa>] kthread+0xea/0x100
[ 167.998078] [<ffffffff817ac6af>] ret_from_fork+0x1f/0x40
[ 167.998081] [<ffffffff8109dd10>] ? kthread_create_on_node+0x1f0/0x1f0
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96293
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
drivers/iommu/iova.c | 31 ++++++++++---------------------
1 file changed, 10 insertions(+), 21 deletions(-)
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index ba764a0835d3..5c5bbdb86a42 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -390,6 +390,11 @@ free_iova(struct iova_domain *iovad, unsigned long pfn)
}
EXPORT_SYMBOL_GPL(free_iova);
+static void free_this_cached_iovas(void *info)
+{
+ free_cpu_cached_iovas(smp_processor_id(), info);
+}
+
/**
* alloc_iova_fast - allocates an iova from rcache
* @iovad: - iova domain in question
@@ -413,15 +418,12 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
retry:
new_iova = alloc_iova(iovad, size, limit_pfn, true);
if (!new_iova) {
- unsigned int cpu;
-
if (flushed_rcache)
return 0;
/* Try replenishing IOVAs by flushing rcache. */
flushed_rcache = true;
- for_each_online_cpu(cpu)
- free_cpu_cached_iovas(cpu, iovad);
+ on_each_cpu(free_this_cached_iovas, iovad, true);
goto retry;
}
@@ -645,7 +647,6 @@ struct iova_magazine {
};
struct iova_cpu_rcache {
- spinlock_t lock;
struct iova_magazine *loaded;
struct iova_magazine *prev;
};
@@ -727,7 +728,6 @@ static void init_iova_rcaches(struct iova_domain *iovad)
continue;
for_each_possible_cpu(cpu) {
cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
- spin_lock_init(&cpu_rcache->lock);
cpu_rcache->loaded = iova_magazine_alloc(GFP_KERNEL);
cpu_rcache->prev = iova_magazine_alloc(GFP_KERNEL);
}
@@ -747,10 +747,9 @@ static bool __iova_rcache_insert(struct iova_domain *iovad,
struct iova_magazine *mag_to_free = NULL;
struct iova_cpu_rcache *cpu_rcache;
bool can_insert = false;
- unsigned long flags;
+ preempt_disable();
cpu_rcache = this_cpu_ptr(rcache->cpu_rcaches);
- spin_lock_irqsave(&cpu_rcache->lock, flags);
if (!iova_magazine_full(cpu_rcache->loaded)) {
can_insert = true;
@@ -778,7 +777,7 @@ static bool __iova_rcache_insert(struct iova_domain *iovad,
if (can_insert)
iova_magazine_push(cpu_rcache->loaded, iova_pfn);
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
+ preempt_enable();
if (mag_to_free) {
iova_magazine_free_pfns(mag_to_free, iovad);
@@ -810,10 +809,9 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache,
struct iova_cpu_rcache *cpu_rcache;
unsigned long iova_pfn = 0;
bool has_pfn = false;
- unsigned long flags;
+ preempt_disable();
cpu_rcache = this_cpu_ptr(rcache->cpu_rcaches);
- spin_lock_irqsave(&cpu_rcache->lock, flags);
if (!iova_magazine_empty(cpu_rcache->loaded)) {
has_pfn = true;
@@ -833,7 +831,7 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache,
if (has_pfn)
iova_pfn = iova_magazine_pop(cpu_rcache->loaded, limit_pfn);
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
+ preempt_enable();
return iova_pfn;
}
@@ -862,17 +860,11 @@ static void free_cpu_iova_rcache(unsigned int cpu, struct iova_domain *iovad,
struct iova_rcache *rcache)
{
struct iova_cpu_rcache *cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
- unsigned long flags;
-
- spin_lock_irqsave(&cpu_rcache->lock, flags);
-
iova_magazine_free_pfns(cpu_rcache->loaded, iovad);
iova_magazine_free(cpu_rcache->loaded);
iova_magazine_free_pfns(cpu_rcache->prev, iovad);
iova_magazine_free(cpu_rcache->prev);
-
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
}
/*
@@ -906,16 +898,13 @@ void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad)
{
struct iova_cpu_rcache *cpu_rcache;
struct iova_rcache *rcache;
- unsigned long flags;
int i;
for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
rcache = &iovad->rcaches[i];
cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
- spin_lock_irqsave(&cpu_rcache->lock, flags);
iova_magazine_free_pfns(cpu_rcache->loaded, iovad);
iova_magazine_free_pfns(cpu_rcache->prev, iovad);
- spin_unlock_irqrestore(&cpu_rcache->lock, flags);
}
}
--
2.8.1