diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-10 19:07:44 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-10 19:07:44 -0700 |
commit | 97d052ea3fa853b9aabcc4baca1a605cb1188611 (patch) | |
tree | 48901cbccafdc5870c7dad9cce98e9338065f8a3 /drivers | |
parent | 086ba2ec163b638abd2a90ef3e8bab0238d02e56 (diff) | |
parent | 0cd39f4600ed4de859383018eb10f0f724900e1b (diff) |
Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
"A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in
various situations caused by the lockdep additions to seqcount to
validate that the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict
per CPU seqcounts. As the lock is not part of the seqcount, lockdep
cannot validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored
and write_seqcount_begin() has a lockdep assertion to validate that
the lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API
is unchanged and determines the type at compile time with the help
of _Generic which is possible now that the minimal GCC version has
been moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs
which have been addressed already independent of this.
While generally useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if
the writers are serialized by an associated lock, which leads to
the well known reader preempts writer livelock. RT prevents this by
storing the associated lock pointer independent of lockdep in the
seqcount and changing the reader side to block on the lock when a
reader detects that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and
initializers"
* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
locking/seqlock, headers: Untangle the spaghetti monster
locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
x86/headers: Remove APIC headers from <asm/smp.h>
seqcount: More consistent seqprop names
seqcount: Compress SEQCNT_LOCKNAME_ZERO()
seqlock: Fold seqcount_LOCKNAME_init() definition
seqlock: Fold seqcount_LOCKNAME_t definition
seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
hrtimer: Use sequence counter with associated raw spinlock
kvm/eventfd: Use sequence counter with associated spinlock
userfaultfd: Use sequence counter with associated spinlock
NFSv4: Use sequence counter with associated spinlock
iocost: Use sequence counter with associated spinlock
raid5: Use sequence counter with associated spinlock
vfs: Use sequence counter with associated spinlock
timekeeping: Use sequence counter with associated raw spinlock
xfrm: policy: Use sequence counters with associated lock
netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
netfilter: conntrack: Use sequence counter with associated spinlock
sched: tasks: Use sequence counter with associated spinlock
...
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/dma-buf/dma-resv.c | 15 | ||||
-rw-r--r-- | drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 | ||||
-rw-r--r-- | drivers/iommu/intel/irq_remapping.c | 1 | ||||
-rw-r--r-- | drivers/md/raid5.c | 2 | ||||
-rw-r--r-- | drivers/md/raid5.h | 2 |
5 files changed, 4 insertions, 18 deletions
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 07f5273207e7..434a3314fb0e 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -52,12 +52,6 @@ DEFINE_WD_CLASS(reservation_ww_class); EXPORT_SYMBOL(reservation_ww_class); -struct lock_class_key reservation_seqcount_class; -EXPORT_SYMBOL(reservation_seqcount_class); - -const char reservation_seqcount_string[] = "reservation_seqcount"; -EXPORT_SYMBOL(reservation_seqcount_string); - /** * dma_resv_list_alloc - allocate fence list * @shared_max: number of fences we need space for @@ -143,9 +137,8 @@ subsys_initcall(dma_resv_lockdep); void dma_resv_init(struct dma_resv *obj) { ww_mutex_init(&obj->lock, &reservation_ww_class); + seqcount_ww_mutex_init(&obj->seq, &obj->lock); - __seqcount_init(&obj->seq, reservation_seqcount_string, - &reservation_seqcount_class); RCU_INIT_POINTER(obj->fence, NULL); RCU_INIT_POINTER(obj->fence_excl, NULL); } @@ -275,7 +268,6 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence) fobj = dma_resv_get_list(obj); count = fobj->shared_count; - preempt_disable(); write_seqcount_begin(&obj->seq); for (i = 0; i < count; ++i) { @@ -297,7 +289,6 @@ replace: smp_store_mb(fobj->shared_count, count); write_seqcount_end(&obj->seq); - preempt_enable(); dma_fence_put(old); } EXPORT_SYMBOL(dma_resv_add_shared_fence); @@ -324,14 +315,12 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence) if (fence) dma_fence_get(fence); - preempt_disable(); write_seqcount_begin(&obj->seq); /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(obj->fence_excl, fence); if (old) old->shared_count = 0; write_seqcount_end(&obj->seq); - preempt_enable(); /* inplace update, no shared fences */ while (i--) @@ -409,13 +398,11 @@ retry: src_list = dma_resv_get_list(dst); old = dma_resv_get_excl(dst); - preempt_disable(); write_seqcount_begin(&dst->seq); /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(dst->fence_excl, new); RCU_INIT_POINTER(dst->fence, dst_list); write_seqcount_end(&dst->seq); - preempt_enable(); dma_resv_list_free(src_list); dma_fence_put(old); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c index e5a5ba869eb4..a58af513c952 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c @@ -258,11 +258,9 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo, new->shared_count = k; /* Install the new fence list, seqcount provides the barriers */ - preempt_disable(); write_seqcount_begin(&resv->seq); RCU_INIT_POINTER(resv->fence, new); write_seqcount_end(&resv->seq); - preempt_enable(); /* Drop the references to the removed fences or move them to ef_list */ for (i = j, k = 0; i < old->shared_count; ++i) { diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c index aa096b333a99..23583b0e66a5 100644 --- a/drivers/iommu/intel/irq_remapping.c +++ b/drivers/iommu/intel/irq_remapping.c @@ -15,6 +15,7 @@ #include <linux/irqdomain.h> #include <linux/crash_dump.h> #include <asm/io_apic.h> +#include <asm/apic.h> #include <asm/smp.h> #include <asm/cpu.h> #include <asm/irq_remapping.h> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index fb8d1fb14088..ef0fd4830803 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -7019,7 +7019,7 @@ static struct r5conf *setup_conf(struct mddev *mddev) } else goto abort; spin_lock_init(&conf->device_lock); - seqcount_init(&conf->gen_lock); + seqcount_spinlock_init(&conf->gen_lock, &conf->device_lock); mutex_init(&conf->cache_size_mutex); init_waitqueue_head(&conf->wait_for_quiescent); init_waitqueue_head(&conf->wait_for_stripe); diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h index 7fb3b26a181a..16fc29472f5c 100644 --- a/drivers/md/raid5.h +++ b/drivers/md/raid5.h @@ -582,7 +582,7 @@ struct r5conf { int prev_chunk_sectors; int prev_algo; short generation; /* increments with every reshape */ - seqcount_t gen_lock; /* lock against generation changes */ + seqcount_spinlock_t gen_lock; /* lock against generation changes */ unsigned long reshape_checkpoint; /* Time we last updated * metadata */ long long min_offset_diff; /* minimum difference between |