Re: [PATCH] Fix SMP support on 3c527 net driver
From: Manfred Spraul
Date: Sun Aug 31 2003 - 12:33:56 EST
Felipe W Damasio wrote:
Hi Manfred,
Manfred Spraul wrote:
Additionally, you must replace the sleep_on calls with wait_event, or
an open-coded wait queue: sleep_on is racy, it only works with cli().
Oh, I didn't no that..
IMHO the right way to fix cli() is
- add a single spinlock to the driver or the device structure. Do not
forget the spin_lock_init().
- replace cli/sti with spin_lock_irqsave/spin_unlock_irqsave.
Yes.
- Additionally acquire the spinlock in every interrupt handler (cli()
stops all interrupts, spinlocks only stop interrupt on the current cpu).
- check if there were recursive cli() calls. Fix them.
- replace all sleep_on calls with wait queue calls.
- check if there are any kmalloc or schedule calls in the area now
under the spinlock, and reorganize the code.
But doesn't wait_queue call schedule()?
Yes, it does. You need a larger change to fix that. Something like the
attached patch.
--
Manfred
--- 2.6/drivers/net/3c527.c 2003-06-17 06:20:03.000000000 +0200
+++ build-2.6/drivers/net/3c527.c 2003-08-31 19:26:37.000000000 +0200
@@ -100,6 +100,7 @@
#include <linux/string.h>
#include <linux/wait.h>
#include <linux/ethtool.h>
+#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include <asm/system.h>
@@ -179,6 +180,7 @@
u16 tx_ring_head; /* index to tx en-queue end */
u16 rx_ring_tail; /* index to rx de-queue end */
+ spinlock_t lock;
};
/* The station (ethernet) address prefix, used for a sanity check. */
@@ -579,6 +581,27 @@
return 0;
}
+/**
+ * wait_exec_pending - sleep until exec_pending reaches a certain value
+ * @lp: m32_local structure describing the target card
+ * @value: value to wait for
+ *
+ * The caller must acquire lp->lock before calling this function, it
+ * temporarily drops the lock when it sleeps.
+ */
+
+static void wait_exec_pending(struct mc32_local *lp, int value)
+{
+ while (lp->exec_pending != value) {
+ DEFINE_WAIT(wait);
+
+ prepare_to_wait(&lp->event, &wait, TASK_UNINTERRUPTIBLE);
+ spin_unlock_irq(&lp->lock);
+ schedule();
+ finish_wait(&lp->event, &wait);
+ spin_lock_irq(&lp->lock);
+ }
+}
/**
* mc32_command - send a command and sleep until completion
@@ -619,14 +642,11 @@
int ret = 0;
/*
- * Wait for a command
+ * Wait until there are no more pending commands
*/
- save_flags(flags);
- cli();
-
- while(lp->exec_pending)
- sleep_on(&lp->event);
+ spin_lock_irqsave(&lp->lock, flags);
+ wait_exec_pending(lp, 0);
/*
* Issue mine
@@ -634,7 +654,7 @@
lp->exec_pending=1;
- restore_flags(flags);
+ spin_unlock_irqrestore(&lp->lock, flags);
lp->exec_box->mbox=0;
lp->exec_box->mbox=cmd;
@@ -645,13 +665,10 @@
while(!(inb(ioaddr+HOST_STATUS)&HOST_STATUS_CRR));
outb(1<<6, ioaddr+HOST_CMD);
- save_flags(flags);
- cli();
-
- while(lp->exec_pending!=2)
- sleep_on(&lp->event);
+ spin_lock_irqsave(&lp->lock, flags);
+ wait_exec_pending(lp, 2);
lp->exec_pending=0;
- restore_flags(flags);
+ spin_unlock_irqrestore(&lp->lock, flags);
if(lp->exec_box->mbox&(1<<13))
ret = -1;