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(new for ppa and imm) Re: [PATCH] Re: Patch to fix lockup on

PATCH Douglas Gilbert 2 participants 2 messages Nov 21, 2000 – Dec 13, 2000 SCSI

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Douglas Gilbert

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Quoted 9 lines · John Cavan
Quoted 8 lines · Tim Waugh
Quoted 3 lines · John Cavan

[...] This patch unlocks, allows the lowlevel driver to do it's probes, and then relocks. It could probably be more granular in the parport_pc code, but my own home tests show it to be working fine.

Is that safe?

Safer than an oops/lockup :-)

Quoted 11 lines

I'm not sure. I know why it causes the NMI lockup, but I'm not enough of an expert to sort it out. I've got a pretty good feel for the Zip driver, but not the parport or scsi code yet, so I don't know how safe it is. The new scsi error stuff does mention that drivers must spinunlock/spinlock if it enables interrupts.

Quoted 2 lines

Also, what bit of the parport code is tripping over the lock? Request_module or something?

During the init phase of the parport_pc module it probes and enables the IRQ(s) of the parallel port, but the scsi layer has them locked.

John and Tim,
At least using imm on my SMP machine (BP6 dual celery) I found that I had to go a bit further than John's patch. Basically I have unlocked the whole of imm_detect(). It was necessary to unblock parport_enumerate() but not sufficient.

Please see attachment. I don't have a ppa device to test. Eric Y. makes some comments just before the (*detect()) call in scsi.c relating to low level driver detect routines.

Doug Gilbert
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drivers/scsi/imm.cx2 renamed from drivers/scsi/imm.c +11 -3
@@ -122,14 +122,17 @@
     struct Scsi_Host *hreg;
     int ports;
     int i, nhosts, try_again;
-    struct parport *pb = parport_enumerate();
+    struct parport *pb;
 
     printk("imm: Version %s\n", IMM_VERSION);
+    spin_unlock_irq(&io_request_lock);
+    pb = parport_enumerate();
     nhosts = 0;
     try_again = 0;
 
     if (!pb) {
 	printk("imm: parport reports no devices.\n");
+        spin_lock_irq(&io_request_lock);
 	return 0;
     }
   retry_entry:

@@ -154,6 +157,7 @@
 		    printk(KERN_ERR "imm%d: failed to claim parport because a "
 		      "pardevice is owning the port for too longtime!\n",
 			   i);
+                    spin_lock_irq(&io_request_lock);
 		    return 0;
 		}
 	    }

@@ -208,12 +212,16 @@
 	nhosts++;
     }
     if (nhosts == 0) {
-	if (try_again == 1)
+	if (try_again == 1) {
+            spin_lock_irq(&io_request_lock);
 	    return 0;
+	}
 	try_again = 1;
 	goto retry_entry;
-    } else
+    } else {
+        spin_lock_irq(&io_request_lock);
 	return 1;		/* return number of hosts detected */
+    }
 }
 
 /* This is to give the imm driver a way to modify the timings (and other

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#1 lore raw

Is the io_request_lock-dropping patch for ppa/imm needed for 2.2.x as well, or is it just a 2.4.x thing?

Tim.
*/