From 89f077ab90d9940b7b74a9a2429940a4af373f79 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 9 Mar 2020 11:09:30 +0000
Subject: [PATCH] drm/i915: Mark up unlocked update of i915_request.hwsp_seqno
Git-commit: 89f077ab90d9940b7b74a9a2429940a4af373f79
Patch-mainline: v5.7-rc1
References: bsc#1174737
During i915_request_retire() we decouple the i915_request.hwsp_seqno
from the intel_timeline so that it may be freed before the request is
released. However, we need to warn the compiler that the pointer may
update under its nose.
[ 171.438899] BUG: KCSAN: data-race in i915_request_await_dma_fence [i915] / i915_request_retire [i915]
[ 171.438920]
[ 171.438932] write to 0xffff8881e7e28ce0 of 8 bytes by task 148 on cpu 2:
[ 171.439174] i915_request_retire+0x1ea/0x660 [i915]
[ 171.439408] retire_requests+0x7a/0xd0 [i915]
[ 171.439640] engine_retire+0xa1/0xe0 [i915]
[ 171.439657] process_one_work+0x3b1/0x690
[ 171.439671] worker_thread+0x80/0x670
[ 171.439685] kthread+0x19a/0x1e0
[ 171.439701] ret_from_fork+0x1f/0x30
[ 171.439721]
[ 171.439739] read to 0xffff8881e7e28ce0 of 8 bytes by task 696 on cpu 1:
[ 171.439990] i915_request_await_dma_fence+0x162/0x520 [i915]
[ 171.440230] i915_request_await_object+0x2fe/0x470 [i915]
[ 171.440467] i915_gem_do_execbuffer+0x45dc/0x4c20 [i915]
[ 171.440704] i915_gem_execbuffer2_ioctl+0x2c3/0x580 [i915]
[ 171.440722] drm_ioctl_kernel+0xe4/0x120
[ 171.440736] drm_ioctl+0x297/0x4c7
[ 171.440750] ksys_ioctl+0x89/0xb0
[ 171.440766] __x64_sys_ioctl+0x42/0x60
[ 171.440788] do_syscall_64+0x6e/0x2c0
[ 171.440802] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200309110934.868-1-chris@chris-wilson.co.uk
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/i915_request.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index d4bae16b4785..6020d5b2a3df 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -396,7 +396,9 @@ static inline bool i915_seqno_passed(u32 seq1, u32 seq2)
static inline u32 __hwsp_seqno(const struct i915_request *rq)
{
- return READ_ONCE(*rq->hwsp_seqno);
+ const u32 *hwsp = READ_ONCE(rq->hwsp_seqno);
+
+ return READ_ONCE(*hwsp);
}
/**
@@ -510,7 +512,8 @@ static inline bool i915_request_completed(const struct i915_request *rq)
static inline void i915_request_mark_complete(struct i915_request *rq)
{
- rq->hwsp_seqno = (u32 *)&rq->fence.seqno; /* decouple from HWSP */
+ WRITE_ONCE(rq->hwsp_seqno, /* decouple from HWSP */
+ (u32 *)&rq->fence.seqno);
}
static inline bool i915_request_has_waitboost(const struct i915_request *rq)
--
2.16.4