leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

dma-buf: Remove custom seqcount lockdep class key

Browse Source 
Commit 3c3b177a93 ("reservation: add support for read-only access
using rcu") introduced a sequence counter to manage updates to
reservations. Back then, the reservation object initializer
reservation_object_init() was always inlined.

Having the sequence counter initialization inlined meant that each of
the call sites would have a different lockdep class key, which would've
broken lockdep's deadlock detection. The aforementioned commit thus
introduced, and exported, a custom seqcount lockdep class key and name.

The commit 8735f16803 ("dma-buf: cleanup reservation_object_init...")
transformed the reservation object initializer to a normal non-inlined C
function. seqcount_init(), which automatically defines the seqcount
lockdep class key and must be called non-inlined, can now be safely used.

Remove the seqcount custom lockdep class key, name, and export. Use
seqcount_init() inside the dma reservation object initializer.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://lkml.kernel.org/r/20200720155530.1173732-12-a.darwish@linutronix.de
This commit is contained in:
Ahmed S. Darwish 2020-07-20 17:55:17 +02:00 committed by Peter Zijlstra
parent ec8702da57
commit 318ce71f3e
2 changed files with 1 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/dma-buf/dma-resv.c
View File

@ -51,12 +51,6 @@
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
@ -135,9 +129,8 @@ subsys_initcall(dma_resv_lockdep);
void dma_resv_init(struct dma_resv *obj)
{
ww_mutex_init(&obj->lock, &reservation_ww_class);
seqcount_init(&obj->seq);
__seqcount_init(&obj->seq, reservation_seqcount_string,
&reservation_seqcount_class);
RCU_INIT_POINTER(obj->fence, NULL);
RCU_INIT_POINTER(obj->fence_excl, NULL);
}

2
include/linux/dma-resv.h
View File

@ -46,8 +46,6 @@
#include <linux/rcupdate.h>
extern struct ww_class reservation_ww_class;
extern struct lock_class_key reservation_seqcount_class;
extern const char reservation_seqcount_string[];
/**
* struct dma_resv_list - a list of shared fences