From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 1/4] locking/ww_mutex: add ww_mutex_is_owned_by function v3 Date: Tue, 20 Feb 2018 14:12:53 +0100 Message-ID: <20180220131253.GF25314@hirez.programming.kicks-ass.net> References: <20180220125829.27060-1-christian.koenig@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <20180220125829.27060-1-christian.koenig@amd.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org List-Id: amd-gfx.lists.freedesktop.org T24gVHVlLCBGZWIgMjAsIDIwMTggYXQgMDE6NTg6MjZQTSArMDEwMCwgQ2hyaXN0aWFuIEvDtm5p ZyB3cm90ZToKPiBhbWRncHUgbmVlZHMgdG8gdmVyaWZ5IGlmIHVzZXJzcGFjZSBzZW5kcyB1cyB2 YWxpZCBhZGRyZXNzZXMgYW5kIHRoZSBzaW1wbGVzdAo+IHdheSBvZiBkb2luZyB0aGlzIGlzIHRv IGNoZWNrIGlmIHRoZSBidWZmZXIgb2JqZWN0IGlzIGxvY2tlZCB3aXRoIHRoZSB0aWNrZXQKPiBv ZiB0aGUgY3VycmVudCBzdWJtaXNzaW9uLgo+IAo+IENsZWFuIHVwIHRoZSBhY2Nlc3MgdG8gdGhl IHd3X211dGV4IGludGVybmFscyBieSBwcm92aWRpbmcgYSBmdW5jdGlvbgo+IGZvciB0aGlzIGFu ZCBleHRlbmQgdGhlIGNoZWNrIHRvIHRoZSB0aHJlYWQgb3duaW5nIHRoZSB1bmRlcmx5aW5nIG11 dGV4LgoKPiBTaWduZWQtb2ZmLWJ5OiBDaHJpc3RpYW4gS8O2bmlnIDxjaHJpc3RpYW4ua29lbmln QGFtZC5jb20+CgpNdWNoIHRoYW5rcyBmb3IgQ2MnaW5nIHRoZSByZWxldmFudCBtYWludGFpbmVy cyA6LwoKPiAtLS0KPiAgaW5jbHVkZS9saW51eC93d19tdXRleC5oIHwgMTcgKysrKysrKysrKysr KysrKysKPiAgMSBmaWxlIGNoYW5nZWQsIDE3IGluc2VydGlvbnMoKykKPiAKPiBkaWZmIC0tZ2l0 IGEvaW5jbHVkZS9saW51eC93d19tdXRleC5oIGIvaW5jbHVkZS9saW51eC93d19tdXRleC5oCj4g aW5kZXggMzlmZGExOTViZjc4Li4xNGU0MTQ5ZDNkOWQgMTAwNjQ0Cj4gLS0tIGEvaW5jbHVkZS9s aW51eC93d19tdXRleC5oCj4gKysrIGIvaW5jbHVkZS9saW51eC93d19tdXRleC5oCj4gQEAgLTM1 OCw0ICszNTgsMjEgQEAgc3RhdGljIGlubGluZSBib29sIHd3X211dGV4X2lzX2xvY2tlZChzdHJ1 Y3Qgd3dfbXV0ZXggKmxvY2spCj4gIAlyZXR1cm4gbXV0ZXhfaXNfbG9ja2VkKCZsb2NrLT5iYXNl KTsKPiAgfQo+ICAKPiArLyoqCj4gKyAqIHd3X211dGV4X2lzX293bmVkX2J5IC0gaXMgdGhlIHcv dyBtdXRleCBsb2NrZWQgYnkgdGhpcyB0YXNrIGluIHRoYXQgY29udGV4dAo+ICsgKiBAbG9jazog dGhlIG11dGV4IHRvIGJlIHF1ZXJpZWQKPiArICogQGN0eDogdGhlIHcvdyBhY3F1aXJlIGNvbnRl eHQgdG8gdGVzdAo+ICsgKgo+ICsgKiBJZiBAY3R4IGlzIG5vdCBOVUxMIHRlc3QgaWYgdGhlIG11 dGV4IGlzIG93bmVkIGJ5IHRoaXMgY29udGV4dC4KPiArICogSWYgQGN0eCBpcyBOVUxMIHRlc3Qg aWYgdGhlIG11dGV4IGlzIG93bmVkIGJ5IHRoZSBjdXJyZW50IHRocmVhZC4KPiArICovCj4gK3N0 YXRpYyBpbmxpbmUgYm9vbCB3d19tdXRleF9pc19vd25lZF9ieShzdHJ1Y3Qgd3dfbXV0ZXggKmxv Y2ssCj4gKwkJCQkJc3RydWN0IHd3X2FjcXVpcmVfY3R4ICpjdHgpCj4gK3sKPiArCWlmIChjdHgp Cj4gKwkJcmV0dXJuIGxpa2VseShSRUFEX09OQ0UobG9jay0+Y3R4KSA9PSBjdHgpOwo+ICsJZWxz ZQo+ICsJCXJldHVybiBsaWtlbHkoX19tdXRleF9vd25lcigmbG9jay0+YmFzZSkgPT0gY3VycmVu dCk7Cj4gK30KCk11Y2ggYmV0dGVyIHRoYW4gdGhlIHByZXZpb3VzIHZlcnNpb24uIElmIHlvdSB3 YW50IHRvIGJpa2Utc2hlZCwgeW91IGNhbgpsZWF2ZSBvdXQgdGhlICdlbHNlJyBhbmQgdW5pbmRl bnQgdGhlIGxhc3QgbGluZS4KCkkgZG8gd29ycnkgYWJvdXQgcG90ZW50aWFsIHVzZXJzIG9mIC5j dHggPSBOVUxMLCB0aG91Z2guIEl0IG1ha2VzIGl0IGZhcgp0b28gZWFzeSB0byBkbyByZWN1cnNp dmUgbG9ja2luZywgd2hpY2ggaXMgc29tZXRoaW5nIHdlIHNob3VsZCBzdHJvbmdseQpkaXNjb3Vy YWdlLgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpkcmkt ZGV2ZWwgbWFpbGluZyBsaXN0CmRyaS1kZXZlbEBsaXN0cy5mcmVlZGVza3RvcC5vcmcKaHR0cHM6 Ly9saXN0cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9saXN0aW5mby9kcmktZGV2ZWwK From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751782AbeBTNNA (ORCPT ); Tue, 20 Feb 2018 08:13:00 -0500 Received: from merlin.infradead.org ([205.233.59.134]:55754 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751587AbeBTNM7 (ORCPT ); Tue, 20 Feb 2018 08:12:59 -0500 Date: Tue, 20 Feb 2018 14:12:53 +0100 From: Peter Zijlstra To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] locking/ww_mutex: add ww_mutex_is_owned_by function v3 Message-ID: <20180220131253.GF25314@hirez.programming.kicks-ass.net> References: <20180220125829.27060-1-christian.koenig@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180220125829.27060-1-christian.koenig@amd.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 20, 2018 at 01:58:26PM +0100, Christian König wrote: > amdgpu needs to verify if userspace sends us valid addresses and the simplest > way of doing this is to check if the buffer object is locked with the ticket > of the current submission. > > Clean up the access to the ww_mutex internals by providing a function > for this and extend the check to the thread owning the underlying mutex. > Signed-off-by: Christian König Much thanks for Cc'ing the relevant maintainers :/ > --- > include/linux/ww_mutex.h | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h > index 39fda195bf78..14e4149d3d9d 100644 > --- a/include/linux/ww_mutex.h > +++ b/include/linux/ww_mutex.h > @@ -358,4 +358,21 @@ static inline bool ww_mutex_is_locked(struct ww_mutex *lock) > return mutex_is_locked(&lock->base); > } > > +/** > + * ww_mutex_is_owned_by - is the w/w mutex locked by this task in that context > + * @lock: the mutex to be queried > + * @ctx: the w/w acquire context to test > + * > + * If @ctx is not NULL test if the mutex is owned by this context. > + * If @ctx is NULL test if the mutex is owned by the current thread. > + */ > +static inline bool ww_mutex_is_owned_by(struct ww_mutex *lock, > + struct ww_acquire_ctx *ctx) > +{ > + if (ctx) > + return likely(READ_ONCE(lock->ctx) == ctx); > + else > + return likely(__mutex_owner(&lock->base) == current); > +} Much better than the previous version. If you want to bike-shed, you can leave out the 'else' and unindent the last line. I do worry about potential users of .ctx = NULL, though. It makes it far too easy to do recursive locking, which is something we should strongly discourage.