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<div class="moz-cite-prefix">Hi AlexBin,<br>
<br>
the answer is ttm_bo_kunmap isn't called at all and yes in the
case of an iomap we leak the address space reserved.<br>
<br>
But that is completely harmless on a 64bit system compared to
leaking the memory backing the address space.<br>
<br>
Using <span style="font-family: Calibri, Arial, Helvetica,
sans-serif, EmojiFont, "Apple Color Emoji",
"Segoe UI Emoji", NotoColorEmoji, "Segoe UI
Symbol", "Android Emoji", EmojiSymbols;
font-size: 16px;"><span>amdgpu_bo_free_kernel() instead of
openly coding it here is probably a good idea.<br>
<br>
Additional to that it's probably a good idea to set the
no_intr flag when reserving kernel BOs. It is impossible to
receive a signal during module load/unload, but it's probably
better to document that in the code as well.<br>
<br>
Regards,<br>
Christian.<br>
</span></span><br>
Am 18.04.2017 um 20:54 schrieb Xie, AlexBin:<br>
</div>
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<div id="divtagdefaultwrapper"
style="font-size:12pt;color:#000000;font-family:Calibri,Arial,Helvetica,sans-serif;"
dir="ltr">
Hi Christian,
<div><br>
</div>
<div>Have you found how/where/when? When you said "<span
style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 16px;">mapping will just</span><span
style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 16px;"> be released a bit later on", you must
know the answer. </span></div>
<div><br>
</div>
<div>It is difficult to prove something does not exist. Anyway,
I will give it a try to prove such "later on" does not exist.</div>
<div><br>
</div>
<div><span>Function ttm_bo_kunmap is the only function to unmap.
To prove this, search <span>ttm_bo_map_iomap, only <span
style="font-family: Calibri, Arial, Helvetica,
sans-serif, EmojiFont, "Apple Color Emoji",
"Segoe UI Emoji", NotoColorEmoji, "Segoe
UI Symbol", "Android Emoji",
EmojiSymbols; font-size: 16px;">ttm_bo_kunmap use this
enum to correctly kunmap.</span></span></span><br>
</div>
<div><span><span><span style="font-family: Calibri, Arial,
Helvetica, sans-serif, EmojiFont, "Apple Color
Emoji", "Segoe UI Emoji", NotoColorEmoji,
"Segoe UI Symbol", "Android Emoji",
EmojiSymbols; font-size: 16px;"><br>
</span></span></span></div>
<div><span><span><span style="font-family: Calibri, Arial,
Helvetica, sans-serif, EmojiFont, "Apple Color
Emoji", "Segoe UI Emoji", NotoColorEmoji,
"Segoe UI Symbol", "Android Emoji",
EmojiSymbols; font-size: 16px;"><span>Function ttm_bo_kunmap
is not called by ttm itself. This is a hint that all
TTM delay delete mechanism or unref mechanism will NOT
kunmap BO later on.</span><br>
</span></span></span></div>
<div><span><span><span style="font-family: Calibri, Arial,
Helvetica, sans-serif, EmojiFont, "Apple Color
Emoji", "Segoe UI Emoji", NotoColorEmoji,
"Segoe UI Symbol", "Android Emoji",
EmojiSymbols; font-size: 16px;"><span><br>
</span></span></span></span></div>
<div><span><span><span style="font-family: Calibri, Arial,
Helvetica, sans-serif, EmojiFont, "Apple Color
Emoji", "Segoe UI Emoji", NotoColorEmoji,
"Segoe UI Symbol", "Android Emoji",
EmojiSymbols; font-size: 16px;"><span><span
style="font-family: Calibri, Arial, Helvetica,
sans-serif, EmojiFont, "Apple Color
Emoji", "Segoe UI Emoji",
NotoColorEmoji, "Segoe UI Symbol",
"Android Emoji", EmojiSymbols; font-size:
16px;">Function </span><span style="font-family:
Calibri, Arial, Helvetica, sans-serif, EmojiFont,
"Apple Color Emoji", "Segoe UI
Emoji", NotoColorEmoji, "Segoe UI
Symbol", "Android Emoji",
EmojiSymbols; font-size: 16px;">ttm_bo_kunmap is
called by AMDGPU function <span>amdgpu_bo_kunmap
and <span>amdgpu_gem_prime_vunmap.</span></span></span><br>
</span></span></span></span></div>
<div><br>
</div>
<div>Search AMDGPU for <span style="font-family: Calibri, Arial,
Helvetica, sans-serif, EmojiFont, "Apple Color
Emoji", "Segoe UI Emoji", NotoColorEmoji,
"Segoe UI Symbol", "Android Emoji",
EmojiSymbols; font-size: 16px;">amdgpu_bo_kunmap.
All matches do not kunmap for scratch VRAM BO. <span>amdgpu_bo_free_kernel
is a suspect but the answer is still NO.</span></span></div>
<div><span style="font-family: Calibri, Arial, Helvetica,
sans-serif, EmojiFont, "Apple Color Emoji",
"Segoe UI Emoji", NotoColorEmoji, "Segoe UI
Symbol", "Android Emoji", EmojiSymbols;
font-size: 16px;"><span><br>
</span></span></div>
<div><span style="font-family: Calibri, Arial, Helvetica,
sans-serif, EmojiFont, "Apple Color Emoji",
"Segoe UI Emoji", NotoColorEmoji, "Segoe UI
Symbol", "Android Emoji", EmojiSymbols;
font-size: 16px;"><span>So all possibilities are searched.
Did I miss anything?</span></span></div>
<div><span style="font-family: Calibri, Arial, Helvetica,
sans-serif, EmojiFont, "Apple Color Emoji",
"Segoe UI Emoji", NotoColorEmoji, "Segoe UI
Symbol", "Android Emoji", EmojiSymbols;
font-size: 16px;"><span><br>
</span></span></div>
<div>Thanks,</div>
<div>Alex Bin Xie</div>
<div><br>
</div>
</div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
color="#000000" face="Calibri, sans-serif"><b>From:</b> Xie,
AlexBin<br>
<b>Sent:</b> Tuesday, April 18, 2017 2:04:33 PM<br>
<b>To:</b> Christian König; Zhou, David(ChunMing);
<a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a><br>
<b>Subject:</b> Re: [PATCH] dmr/amdgpu: Fix wrongly unref of
BO</font>
<div> </div>
</div>
<div>
<div id="divtagdefaultwrapper"
style="font-size:12pt;color:#000000;font-family:Calibri,Arial,Helvetica,sans-serif;"
dir="ltr">
<p>Hi Christian,</p>
<p><br>
</p>
<p>Would you point out where/when will kunmap happen for this
BO when release? <span style="font-size: 12pt;">It must be
somewhere </span><span style="font-size: 12pt;"></span><span
style="font-size: 12pt;">in some function calls</span><span
style="font-size: 12pt;">.</span></p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p><span style="font-size: 12pt;">I checked before I asked for
review. But I did not see such obvious kunmap function
call.</span></p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p><span style="font-size: 12pt;">If so, there should be a
comment in function <span>amdgpu_vram_scratch_fini </span>to
avoid future confusion.</span></p>
<br>
Thanks,
<div>Alex Bin Xie<br>
<div style="color: rgb(0, 0, 0);">
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="divRplyFwdMsg" dir="ltr"><font
style="font-size:11pt" color="#000000" face="Calibri,
sans-serif"><b>From:</b> Christian König
<a class="moz-txt-link-rfc2396E" href="mailto:deathsimple@vodafone.de"><deathsimple@vodafone.de></a><br>
<b>Sent:</b> Tuesday, April 18, 2017 1:46 PM<br>
<b>To:</b> Xie, AlexBin; Zhou, David(ChunMing);
<a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a><br>
<b>Subject:</b> Re: [PATCH] dmr/amdgpu: Fix wrongly
unref of BO</font>
<div> </div>
</div>
<div>
<div class="moz-cite-prefix">Hi AlexBin,<br>
<br>
No, David is right. This is a very common coding
pattern in the kernel module.<br>
<br>
Freeing up a BO while there still exists a kernel
mapping is perfectly ok, the mapping will just be
released a bit later on.<br>
<br>
So this code is actually perfectly ok and just an
optimization, but your patch breaks it and creates a
memory leak.<br>
<br>
Regards,<br>
Christian.<br>
<br>
Am 18.04.2017 um 17:17 schrieb Xie, AlexBin:<br>
</div>
<blockquote type="cite">
<div id="divtagdefaultwrapper" dir="ltr"
style="font-size:12pt; color:#000000;
font-family:Calibri,Arial,Helvetica,sans-serif">
<p>Hi David,</p>
<p><br>
</p>
<p>When <span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif">amdgpu_bo_reserve
return errors, we cannot release the BO. This is
not a memory leak. General speaking, memory leak
is unnoticed and unintentional.</span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><br>
</span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif">The
caller of function <span>amdgpu_vram_scratch_fini
ignores the return error value...</span></span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><span><br>
</span></span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><span>The
"memory leak" is not caused by my patch. It is
caused because reserving BO fails.</span></span></p>
<p><span
style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt"><br>
</span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><span></span></span><span
style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">This patch
only aim to make function </span><span
style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt">amdgpu_vram_scratch_fini behave
correctly.</span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><span><br>
</span></span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><span>To
follow up, we can add a warning message when
<span
style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:16px">amdgpu_bo_reserve</span>
error happens in a different patch.</span></span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><span><br>
</span></span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif">If
function call </span><span
style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt">amdgpu_bo_reserve is changed to
uninterruptible, this changes driver behaviour.
Without a substantial issue, I would be cautious
for such a change.</span></p>
<p><span style="font-size:12pt;
font-family:Calibri,Arial,Helvetica,sans-serif"><br>
</span></p>
<p>Thanks,</p>
<p>Alex Bin Xie</p>
<br>
<div style="color:rgb(0,0,0)">
<hr tabindex="-1" style="display:inline-block;
width:98%">
<div id="divRplyFwdMsg" dir="ltr"><font
style="font-size:11pt" color="#000000"
face="Calibri, sans-serif"><b>From:</b> Zhou,
David(ChunMing)<br>
<b>Sent:</b> Monday, April 17, 2017 10:38 PM<br>
<b>To:</b> Xie, AlexBin; <a
moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:amd-gfx@lists.freedesktop.org">
amd-gfx@lists.freedesktop.org</a><br>
<b>Subject:</b> Re: [PATCH] dmr/amdgpu: Fix
wrongly unref of BO</font>
<div> </div>
</div>
<div><br>
<br>
<div class="moz-cite-prefix">On 2017年04月17日
22:54, Xie, AlexBin wrote:<br>
</div>
<blockquote type="cite">
<div id="divtagdefaultwrapper" dir="ltr"
style="font-size:12pt; color:#000000;
font-family:Calibri,Arial,Helvetica,sans-serif">
<p>Hi David,</p>
<p><br>
</p>
<p>Thanks for the comments. However, please
have look at <span style="">amdgpu_bo_reserve</span>
definition.</p>
<p><span>static inline int
amdgpu_bo_reserve(struct amdgpu_bo *bo,
bool no_intr)</span><br>
</p>
</div>
</blockquote>
Ah, this is a wired wrapper for ttm_bo_reserve.<br>
<br>
<blockquote type="cite">
<div id="divtagdefaultwrapper" dir="ltr"
style="font-size:12pt; color:#000000;
font-family:Calibri,Arial,Helvetica,sans-serif">
<p><span><br>
</span></p>
<p><span>When we call this function like the
following:</span></p>
<p><span><span style=""> r =
amdgpu_bo_reserve(adev->vram_scratch.robj,
false);</span><br style="">
</span><span style="font-size:12pt">The
false means <span>interruptible</span>.</span><span><br>
</span></p>
<p><span style="font-size:12pt"><br>
</span></p>
<p><span style="font-size:12pt">On the other
hand, when <span style="">amdgpu_bo_reserve
function return error, why do we unref
BO without kunmap and unpin the BO?
This is wrong implementation when <span
style="">amdgpu_bo_reserve return
any error.</span></span></span></p>
</div>
</blockquote>
Yeah, I see your mean, it's in driver
un-loading, How about changing to no
interruptible? Your patch will make a memleak if
bo_reserve fails, but it seems not matter. I
have no strong preference.<br>
<br>
Regards,<br>
David Zhou<br>
<blockquote type="cite">
<div id="divtagdefaultwrapper" dir="ltr"
style="font-size:12pt; color:#000000;
font-family:Calibri,Arial,Helvetica,sans-serif">
<p><br>
</p>
Thanks,
<div>Alex Bin Xie<br>
<br>
<div style="color:rgb(0,0,0)">
<div>
<hr tabindex="-1"
style="display:inline-block;
width:98%">
<div id="x_divRplyFwdMsg" dir="ltr"><font
style="font-size:11pt"
color="#000000" face="Calibri,
sans-serif"><b>From:</b> Zhou,
David(ChunMing)<br>
<b>Sent:</b> Friday, April 14,
2017 12:00 AM<br>
<b>To:</b> Xie, AlexBin; <a
moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:amd-gfx@lists.freedesktop.org">
amd-gfx@lists.freedesktop.org</a><br>
<b>Subject:</b> Re: [PATCH]
dmr/amdgpu: Fix wrongly unref of
BO</font>
<div> </div>
</div>
</div>
<font size="2"><span
style="font-size:10pt">
<div class="PlainText"><br>
<br>
On 2017年04月14日 05:34, Alex Xie
wrote:<br>
> According to comment of
amdgpu_bo_reserve,
amdgpu_bo_reserve<br>
> can return with -ERESTARTSYS.
When this function was interrupted<br>
> by a signal, BO should not be
unref. Otherwise the BO might be<br>
> released while is kmapped and
pinned, or BO MIGHT be deref<br>
> multiple times, etc.<br>
r =
amdgpu_bo_reserve(adev->vram_scratch.robj,
false);<br>
we have specified interruptible to
false, so -ERESTARTSYS isn't
possible <br>
here.<br>
<br>
Thanks,<br>
David Zhou<br>
><br>
> Change-Id:
If76071a768950a0d3ad9d5da7fcae04881807621<br>
> Signed-off-by: Alex Xie <a
moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:AlexBin.Xie@amd.com">
<AlexBin.Xie@amd.com></a><br>
> ---<br>
>
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
| 2 +-<br>
> 1 file changed, 1
insertion(+), 1 deletion(-)<br>
><br>
> diff --git
a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c<br>
> index 53996e3..1dcc2d1 100644<br>
> ---
a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c<br>
> +++
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c<br>
> @@ -355,8 +355,8 @@ static
void
amdgpu_vram_scratch_fini(struct
amdgpu_device *adev)<br>
>
amdgpu_bo_kunmap(adev->vram_scratch.robj);<br>
>
amdgpu_bo_unpin(adev->vram_scratch.robj);<br>
>
amdgpu_bo_unreserve(adev->vram_scratch.robj);<br>
> +
amdgpu_bo_unref(&adev->vram_scratch.robj);<br>
> }<br>
> -
amdgpu_bo_unref(&adev->vram_scratch.robj);<br>
> }<br>
> <br>
> /**<br>
<br>
</div>
</span></font></div>
</div>
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</blockquote>
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