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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: wWl7N+jfxRK6iutNfNTeGLHehpD9eQSWHgOqnALP3vGU0KKv+V8vtieyHBjkLK+Vjk56+BlxDpaMv8EPCvPYorJWREE9R4nhjBFjU+qVkR3zTI062PAmEd8rewn+ZsCOqkoTHUAvmmU85fxwc0gj/QnsOQT8RCXemBiO5246Pcb358VlPFkqWedtYdTDejgj8qpmTLxDhNUm6WxvptCOFo85bdZ8u89pqIwm3TLqBrGkvsLi45QNgaZOD8S0R7r28IbHuYfPJKAm3b2Rbitp9tjGRoXEwSp0IbUSF0q7zg35utsnktQUQS2ETQ9L4X6o7/3RVrr/qd/mpyL3MMAZI2Qp2C7IMNZFL71JUSII6S1xkuy8sLyEhKzrbvRYIFuyepDIFA4bW1CR66hkN8JgBOpcFDJyHX1TaMSXHkywR8jcagSYjBptzIbEDtZ/fW20 X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jul 2026 19:53:59.6935 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 402fad40-09bd-4821-0752-08dee8f42378 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: AM2PEPF0001C712.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS2PR08MB8746 On Thu, Jul 23, 2026 at 11:57:58AM -0400, Adam Young wrote: > > On 7/23/26 05:16, Sudeep Holla wrote: > > On Wed, Jul 22, 2026 at 11:10:51PM -0400, Adam Young wrote: > > > + /* > > > + * Set chan_in_use before ringing the doorbell so a fast completion > > > + * interrupt is not mistaken for a shared interrupt from another > > > + * subspace. Use WRITE_ONCE() for the lockless flag update. The > > > + * ordered MMIO accessor used to ring the doorbell keeps this store > > > + * visible before the platform is notified. > > > + */ > > > + if (pchan->plat_irq > 0) > > > + WRITE_ONCE(pchan->chan_in_use, true); > > > ret = pcc_chan_reg_read_modify_write(&pchan->db); > > > if (!ret && pchan->plat_irq > 0) > > > - pchan->chan_in_use = true; > > > + WRITE_ONCE(pchan->chan_in_use, false); > > > return ret; > > > } > > > -- > > > 2.43.0 > > > iAt the end of the above code, > > > WRITE_ONCE(pchan->chan_in_use, false); > > > should be > > > WRITE_ONCE(pchan->chan_in_use, true); > > > > > > In order to keep the original semantics. The flag is cleared when the > > > messages is ACKed, not here. This version causes a hang. > > > > > Did you run and seeing hang or just code inspection. If latter, have you > > considered that modified code sets it true before doorbell is rung and > > set to false only if there is a failure to ring the doorbell ? > > > Yes, I saw the hang, and debugged to see this line semantically different.  > I changed it to true and things resumed working.  !ret is 0  so that happens > in the success case. > My mistake, I must pay more attention 🙁. I wanted it to be error case and always read it as if(ret..) instead of if(!ret..), sorry for that. -- Regards, Sudeep