diff options
| author | Sumit Saxena | 2021-09-29 18:10:20 +0530 |
|---|---|---|
| committer | Martin K. Petersen | 2021-10-04 23:20:09 -0400 |
| commit | e7dcc514a49e74051b869697d5ab0370f6301d57 (patch) | |
| tree | 5eff60ebc604f6e767becf88c2138a3217848e65 | |
| parent | d4996c6eac4c81b8872043e9391563f67f13e406 (diff) | |
scsi: megaraid_sas: Fix concurrent access to ISR between IRQ polling and real interrupt
IRQ polling thread calls ISR after enable_irq() to handle any missed I/O
completion. The atomic flag "in_used" was added to have the synchronization
between the IRQ polling thread and the interrupt context. There is a bug
around it leading to a race condition.
Below is the sequence:
- IRQ polling thread accesses ISR, fetches the reply descriptor.
- Real interrupt arrives and pre-empts polling thread (enable_irq() is
already called).
- Interrupt context picks the same reply descriptor as fetched by polling
thread, processes it, and exits.
- Polling thread resumes and processes the descriptor which is already
processed by interrupt thread leads to kernel crash.
Setting the "in_used" flag before fetching the reply descriptor ensures
synchronized access to ISR.
Link: https://www.spinics.net/lists/linux-scsi/msg159440.html
Link: https://lore.kernel.org/r/20210929124022.24605-2-sumit.saxena@broadcom.com
Fixes: 9bedd36e9146 ("scsi: megaraid_sas: Handle missing interrupts while re-enabling IRQs")
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
| -rw-r--r-- | drivers/scsi/megaraid/megaraid_sas_fusion.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c index 26d0cf9353dd..eb5ceb75a15e 100644 --- a/drivers/scsi/megaraid/megaraid_sas_fusion.c +++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c @@ -3530,6 +3530,9 @@ complete_cmd_fusion(struct megasas_instance *instance, u32 MSIxIndex, if (atomic_read(&instance->adprecovery) == MEGASAS_HW_CRITICAL_ERROR) return IRQ_HANDLED; + if (irq_context && !atomic_add_unless(&irq_context->in_used, 1, 1)) + return 0; + desc = fusion->reply_frames_desc[MSIxIndex] + fusion->last_reply_idx[MSIxIndex]; @@ -3540,11 +3543,11 @@ complete_cmd_fusion(struct megasas_instance *instance, u32 MSIxIndex, reply_descript_type = reply_desc->ReplyFlags & MPI2_RPY_DESCRIPT_FLAGS_TYPE_MASK; - if (reply_descript_type == MPI2_RPY_DESCRIPT_FLAGS_UNUSED) + if (reply_descript_type == MPI2_RPY_DESCRIPT_FLAGS_UNUSED) { + if (irq_context) + atomic_dec(&irq_context->in_used); return IRQ_NONE; - - if (irq_context && !atomic_add_unless(&irq_context->in_used, 1, 1)) - return 0; + } num_completed = 0; |