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Sun, 25 Jan 2026 04:18:55 -0800 (PST) From: chengkaitao To: kashyap.desai@broadcom.com, sumit.saxena@broadcom.com, shivasharan.srikanteshwara@broadcom.com, chandrakanth.patil@broadcom.com, James.Bottomley@HansenPartnership.com, martin.petersen@oracle.com Cc: megaraidlinux.pdl@broadcom.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Chengkaitao Subject: [RFC 1/2] megaraid: Fix the issue of erroneous reset of Words in reply_desc Date: Sun, 25 Jan 2026 20:18:41 +0800 Message-ID: <20260125121842.79839-2-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260125121842.79839-1-pilgrimtao@gmail.com> References: <20260125121842.79839-1-pilgrimtao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Chengkaitao The following panic occurred on kernel 6.6 (arch: loongarch): Call Trace: complete_cmd_fusion+0x180/0x7c8 [megaraid_sas] megasas_isr_fusion+0xd4/0xf0 [megaraid_sas] __handle_irq_event_percpu+0x70/0x228 handle_irq_event+0x44/0xf8 handle_edge_irq+0xe8/0x328 avecintc_irq_dispatch+0x68/0x120 handle_irq_desc+0x5c/0x78 handle_cpu_irq+0x6c/0xa8 handle_loongarch_irq+0x2c/0x48 do_vint+0x7c/0xd0 sched_update_worker+0x8/0x90 worker_thread+0x218/0x480 kthread+0xf0/0xf8 ret_from_kernel_thread+0x28/0xc8 ret_from_kernel_thread_asm+0xc/0xa0 Observed symptoms during the issue: complete_cmd_fusion(struct megasas_instance *instance, u32 MSIxIndex, struct megasas_irq_context *irq_context) { ****** while (d_val.u.low !=3D cpu_to_le32(UINT_MAX) && d_val.u.high !=3D cpu_to_le32(UINT_MAX)) { /** When the issue occurs: d_val.u.low =3D=3D 60293120 d_val.u.high =3D=3D 0 reply_desc->SMID =3D=3D 0xffff **/ smid =3D le16_to_cpu(reply_desc->SMID); cmd_fusion =3D fusion->cmd_list[smid - 1]; scsi_io_req =3D (struct MPI2_RAID_SCSI_IO_REQUEST *) cmd_fusion->io_request; /** cmd_fusion becomes an invalid pointer **/ ****** } In the complete_cmd_fusion function, the following assignment exists: d_val.word =3D desc->Words; Thus, reply_desc->SMID =3D=3D 0xffff may be caused by a concurrency-related corruption. Reproduction probability is very low. After code review, I suspect the following race condition scenario: interrupt(complete_cmd_fusion) cpu1(megasas_reset_reply_desc) while (d_val.u.low !=3D *****) { scsi_io_req =3D cmd_fusion->io_request; d_val.word =3D desc->Words; reply_desc->Words =3D cpu_to_le64(ULLONG_MAX); } Note: This is a proposed patch for discussion only. It has not been verified to resolve the issue. If you have alternative suggestions, please join the discussion. Signed-off-by: Chengkaitao --- drivers/scsi/megaraid/megaraid_sas_fusion.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/meg= araid/megaraid_sas_fusion.c index a6794f49e9fa..3d3480b19734 100644 --- a/drivers/scsi/megaraid/megaraid_sas_fusion.c +++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c @@ -4282,16 +4282,23 @@ void megasas_reset_reply_desc(struct megasas_insta= nce *instance) int i, j, count; struct fusion_context *fusion; union MPI2_REPLY_DESCRIPTORS_UNION *reply_desc; + struct megasas_irq_context *irq_context; =20 fusion =3D instance->ctrl_context; count =3D instance->msix_vectors > 0 ? instance->msix_vectors : 1; count +=3D instance->iopoll_q_count; =20 for (i =3D 0 ; i < count ; i++) { + irq_context =3D &instance->irq_context[i]; + while (!access_irq_context(irq_context)) + cpu_relax(); + fusion->last_reply_idx[i] =3D 0; reply_desc =3D fusion->reply_frames_desc[i]; for (j =3D 0 ; j < fusion->reply_q_depth; j++, reply_desc++) reply_desc->Words =3D cpu_to_le64(ULLONG_MAX); + + release_irq_context(irq_context); } } =20 --=20 2.50.1 (Apple Git-155)