From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [PATCH] drm: Make drm_read() more robust against multithreaded races Date: Fri, 05 Dec 2014 09:42:35 +0100 Message-ID: References: <1417727005-26301-1-git-send-email-chris@chris-wilson.co.uk> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <1417727005-26301-1-git-send-email-chris@chris-wilson.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Chris Wilson Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org QXQgVGh1LCAgNCBEZWMgMjAxNCAyMTowMzoyNSArMDAwMCwKQ2hyaXMgV2lsc29uIHdyb3RlOgo+ IAo+IFRoZSBjdXJyZW50IGltcGxlbWVudGF0aW9uIG9mIGRybV9yZWFkKCkgZmFjZXMgYSBudW1i ZXIgb2YgaXNzdWVzOgo+IAo+IDEuIFVwb24gYW4gZXJyb3IsIGl0IGNvbnN1bWVzIHRoZSBldmVu dCB3aGljaCBtYXkgbGVhZCB0byB0aGUgY2xpZW50Cj4gYmxvY2tpbmcuCj4gMi4gVXBvbiBhbiBl cnJvciwgaXQgZm9yZ2V0cyBhYm91dCBldmVudHMgYWxyZWFkeSBjb3BpZWQKPiAzLiBJZiBpdCBm YWlscyB0byBjb3B5IGEgc2luZ2xlIGV2ZW50IHdpdGggT19OT05CTE9DSyBpdCBmYWxscyBpbnRv IGEKPiBpbmZpbml0ZSBsb29wIG9mIHJlcG9ydGluZyBFQUdBSU4uCj4gMy4gVGhlcmUgaXMgYSBy YWNlIGJldHdlZW4gbXVsdGlwbGUgd2FpdGVycyBhbmQgYmxvY2tpbmcgcmVhZHMgb2YgdGhlCj4g ZXZlbnRzIGxpc3QuCj4gCj4gSGVyZSwgd2UgaW5saW5lIGRybV9kZXF1ZXVlX2V2ZW50KCkgaW50 byBkcm1fcmVhZCgpIHNvIHRoYXQgd2UgY2FuIHRha2UKPiB0aGUgc3BpbmxvY2sgYXJvdW5kIHRo ZSBsaXN0IHdhbGtpbmcgYW5kIGV2ZW50IGNvcHlpbmcsIGFuZCBpbXBvcnRhbnRseQo+IHJlb3Jk ZXIgdGhlIGVycm9yIGhhbmRsaW5nIHRvIGF2b2lkIHRoZSBpc3N1ZXMgYWJvdmUuCj4gCj4gQ2M6 IFRha2FzaGkgSXdhaSA8dGl3YWlAc3VzZS5kZT4KClJldmlld2VkLWJ5OiBUYWthc2hpIEl3YWkg PHRpd2FpQHN1c2UuZGU+CgoKVGFrYXNoaQoKPiBTaWduZWQtb2ZmLWJ5OiBDaHJpcyBXaWxzb24g PGNocmlzQGNocmlzLXdpbHNvbi5jby51az4KPiAtLS0KPiAgZHJpdmVycy9ncHUvZHJtL2RybV9m b3BzLmMgfCA5MCArKysrKysrKysrKysrKysrKysrKysrLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0t Cj4gIDEgZmlsZSBjaGFuZ2VkLCA0MyBpbnNlcnRpb25zKCspLCA0NyBkZWxldGlvbnMoLSkKPiAK PiBkaWZmIC0tZ2l0IGEvZHJpdmVycy9ncHUvZHJtL2RybV9mb3BzLmMgYi9kcml2ZXJzL2dwdS9k cm0vZHJtX2ZvcHMuYwo+IGluZGV4IDkxZTExMDVmMjgwMC4uMDc2ZGQ2MDZiNTgwIDEwMDY0NAo+ IC0tLSBhL2RyaXZlcnMvZ3B1L2RybS9kcm1fZm9wcy5jCj4gKysrIGIvZHJpdmVycy9ncHUvZHJt L2RybV9mb3BzLmMKPiBAQCAtNDc4LDYzICs0NzgsNTkgQEAgaW50IGRybV9yZWxlYXNlKHN0cnVj dCBpbm9kZSAqaW5vZGUsIHN0cnVjdCBmaWxlICpmaWxwKQo+ICB9Cj4gIEVYUE9SVF9TWU1CT0wo ZHJtX3JlbGVhc2UpOwo+ICAKPiAtc3RhdGljIGJvb2wKPiAtZHJtX2RlcXVldWVfZXZlbnQoc3Ry dWN0IGRybV9maWxlICpmaWxlX3ByaXYsCj4gLQkJICBzaXplX3QgdG90YWwsIHNpemVfdCBtYXgs IHN0cnVjdCBkcm1fcGVuZGluZ19ldmVudCAqKm91dCkKPiArc3NpemVfdCBkcm1fcmVhZChzdHJ1 Y3QgZmlsZSAqZmlscCwgY2hhciBfX3VzZXIgKmJ1ZmZlciwKPiArCQkgc2l6ZV90IGNvdW50LCBs b2ZmX3QgKm9mZnNldCkKPiAgewo+ICsJc3RydWN0IGRybV9maWxlICpmaWxlX3ByaXYgPSBmaWxw LT5wcml2YXRlX2RhdGE7Cj4gIAlzdHJ1Y3QgZHJtX2RldmljZSAqZGV2ID0gZmlsZV9wcml2LT5t aW5vci0+ZGV2Owo+IC0Jc3RydWN0IGRybV9wZW5kaW5nX2V2ZW50ICplOwo+IC0JdW5zaWduZWQg bG9uZyBmbGFnczsKPiAtCWJvb2wgcmV0ID0gZmFsc2U7Cj4gLQo+IC0Jc3Bpbl9sb2NrX2lycXNh dmUoJmRldi0+ZXZlbnRfbG9jaywgZmxhZ3MpOwo+ICsJc3NpemVfdCByZXQgPSAwOwo+ICAKPiAt CSpvdXQgPSBOVUxMOwo+IC0JaWYgKGxpc3RfZW1wdHkoJmZpbGVfcHJpdi0+ZXZlbnRfbGlzdCkp Cj4gLQkJZ290byBvdXQ7Cj4gLQllID0gbGlzdF9maXJzdF9lbnRyeSgmZmlsZV9wcml2LT5ldmVu dF9saXN0LAo+IC0JCQkgICAgIHN0cnVjdCBkcm1fcGVuZGluZ19ldmVudCwgbGluayk7Cj4gLQlp ZiAoZS0+ZXZlbnQtPmxlbmd0aCArIHRvdGFsID4gbWF4KQo+IC0JCWdvdG8gb3V0Owo+ICsJaWYg KCFhY2Nlc3Nfb2soVkVSSUZZX1dSSVRFLCBidWZmZXIsIGNvdW50KSkKPiArCQlyZXR1cm4gLUVG QVVMVDsKPiAgCj4gLQlmaWxlX3ByaXYtPmV2ZW50X3NwYWNlICs9IGUtPmV2ZW50LT5sZW5ndGg7 Cj4gLQlsaXN0X2RlbCgmZS0+bGluayk7Cj4gLQkqb3V0ID0gZTsKPiAtCXJldCA9IHRydWU7Cj4g KwlzcGluX2xvY2tfaXJxKCZkZXYtPmV2ZW50X2xvY2spOwo+ICsJZm9yICg7Oykgewo+ICsJCWlm IChsaXN0X2VtcHR5KCZmaWxlX3ByaXYtPmV2ZW50X2xpc3QpKSB7Cj4gKwkJCWlmIChyZXQpCj4g KwkJCQlicmVhazsKPiAgCj4gLW91dDoKPiAtCXNwaW5fdW5sb2NrX2lycXJlc3RvcmUoJmRldi0+ ZXZlbnRfbG9jaywgZmxhZ3MpOwo+IC0JcmV0dXJuIHJldDsKPiAtfQo+IC0KPiAtc3NpemVfdCBk cm1fcmVhZChzdHJ1Y3QgZmlsZSAqZmlscCwgY2hhciBfX3VzZXIgKmJ1ZmZlciwKPiAtCQkgc2l6 ZV90IGNvdW50LCBsb2ZmX3QgKm9mZnNldCkKPiAtewo+IC0Jc3RydWN0IGRybV9maWxlICpmaWxl X3ByaXYgPSBmaWxwLT5wcml2YXRlX2RhdGE7Cj4gLQlzdHJ1Y3QgZHJtX3BlbmRpbmdfZXZlbnQg KmU7Cj4gLQlzaXplX3QgdG90YWw7Cj4gLQlzc2l6ZV90IHJldDsKPiArCQkJaWYgKGZpbHAtPmZf ZmxhZ3MgJiBPX05PTkJMT0NLKSB7Cj4gKwkJCQlyZXQgPSAtRUFHQUlOOwo+ICsJCQkJYnJlYWs7 Cj4gKwkJCX0KPiAgCj4gLQlpZiAoKGZpbHAtPmZfZmxhZ3MgJiBPX05PTkJMT0NLKSA9PSAwKSB7 Cj4gLQkJcmV0ID0gd2FpdF9ldmVudF9pbnRlcnJ1cHRpYmxlKGZpbGVfcHJpdi0+ZXZlbnRfd2Fp dCwKPiAtCQkJCQkgICAgICAgIWxpc3RfZW1wdHkoJmZpbGVfcHJpdi0+ZXZlbnRfbGlzdCkpOwo+ IC0JCWlmIChyZXQgPCAwKQo+IC0JCQlyZXR1cm4gcmV0Owo+IC0JfQo+ICsJCQlzcGluX3VubG9j a19pcnEoJmRldi0+ZXZlbnRfbG9jayk7Cj4gKwkJCXJldCA9IHdhaXRfZXZlbnRfaW50ZXJydXB0 aWJsZShmaWxlX3ByaXYtPmV2ZW50X3dhaXQsCj4gKwkJCQkJCSAgICAgICAhbGlzdF9lbXB0eSgm ZmlsZV9wcml2LT5ldmVudF9saXN0KSk7Cj4gKwkJCXNwaW5fbG9ja19pcnEoJmRldi0+ZXZlbnRf bG9jayk7Cj4gKwkJCWlmIChyZXQgPCAwKQo+ICsJCQkJYnJlYWs7Cj4gKwo+ICsJCQlyZXQgPSAw Owo+ICsJCX0gZWxzZSB7Cj4gKwkJCXN0cnVjdCBkcm1fcGVuZGluZ19ldmVudCAqZTsKPiArCj4g KwkJCWUgPSBsaXN0X2ZpcnN0X2VudHJ5KCZmaWxlX3ByaXYtPmV2ZW50X2xpc3QsCj4gKwkJCQkJ ICAgICBzdHJ1Y3QgZHJtX3BlbmRpbmdfZXZlbnQsIGxpbmspOwo+ICsJCQlpZiAoZS0+ZXZlbnQt Pmxlbmd0aCArIHJldCA+IGNvdW50KQo+ICsJCQkJYnJlYWs7Cj4gKwo+ICsJCQlpZiAoX19jb3B5 X3RvX3VzZXJfaW5hdG9taWMoYnVmZmVyICsgcmV0LAo+ICsJCQkJCQkgICAgZS0+ZXZlbnQsIGUt PmV2ZW50LT5sZW5ndGgpKSB7Cj4gKwkJCQlpZiAocmV0ID09IDApCj4gKwkJCQkJcmV0ID0gLUVG QVVMVDsKPiArCQkJCWJyZWFrOwo+ICsJCQl9Cj4gIAo+IC0JdG90YWwgPSAwOwo+IC0Jd2hpbGUg KGRybV9kZXF1ZXVlX2V2ZW50KGZpbGVfcHJpdiwgdG90YWwsIGNvdW50LCAmZSkpIHsKPiAtCQlp ZiAoY29weV90b191c2VyKGJ1ZmZlciArIHRvdGFsLAo+IC0JCQkJIGUtPmV2ZW50LCBlLT5ldmVu dC0+bGVuZ3RoKSkgewo+IC0JCQl0b3RhbCA9IC1FRkFVTFQ7Cj4gLQkJCWJyZWFrOwo+ICsJCQlm aWxlX3ByaXYtPmV2ZW50X3NwYWNlICs9IGUtPmV2ZW50LT5sZW5ndGg7Cj4gKwkJCXJldCArPSBl LT5ldmVudC0+bGVuZ3RoOwo+ICsJCQlsaXN0X2RlbCgmZS0+bGluayk7Cj4gKwkJCWUtPmRlc3Ry b3koZSk7Cj4gIAkJfQo+IC0KPiAtCQl0b3RhbCArPSBlLT5ldmVudC0+bGVuZ3RoOwo+IC0JCWUt PmRlc3Ryb3koZSk7Cj4gIAl9Cj4gKwlzcGluX3VubG9ja19pcnEoJmRldi0+ZXZlbnRfbG9jayk7 Cj4gIAo+IC0JcmV0dXJuIHRvdGFsID86IC1FQUdBSU47Cj4gKwlyZXR1cm4gcmV0Owo+ICB9Cj4g IEVYUE9SVF9TWU1CT0woZHJtX3JlYWQpOwo+ICAKPiAtLSAKPiAyLjEuMwo+IApfX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpJbnRlbC1nZnggbWFpbGluZyBs aXN0CkludGVsLWdmeEBsaXN0cy5mcmVlZGVza3RvcC5vcmcKaHR0cDovL2xpc3RzLmZyZWVkZXNr dG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2ludGVsLWdmeAo=