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Subject[PATCH] mwave locking (was: IA32 - 1 New warnings)
John wrote:

>drivers/char/mwave/mwavedd.c:331:2: warning: #warning "Sleeping on spinlock"
>
>
Interesting locking strategy:
A spinlock is placed on the stack and then
spin_lock_irqsave(&local_lock, flags).

Attached is a patch that removes that. Untested due to lack of hardware.
Anyone around such hardware (IBM Thinkpad?)
--
Manfred
--- 2.6/drivers/char/mwave/mwavedd.c 2003-09-07 12:29:10.000000000 +0200
+++ build-2.6/drivers/char/mwave/mwavedd.c 2003-09-07 15:04:00.000000000 +0200
@@ -293,8 +293,6 @@

case IOCTL_MW_GET_IPC: {
unsigned int ipcnum = (unsigned int) ioarg;
- spinlock_t ipc_lock = SPIN_LOCK_UNLOCKED;
- unsigned long flags;

PRINTK_3(TRACE_MWAVE,
"mwavedd::mwave_ioctl IOCTL_MW_GET_IPC"
@@ -310,32 +308,29 @@
}

if (pDrvData->IPCs[ipcnum].bIsEnabled == TRUE) {
+ DECLARE_WAITQUEUE(wait, current);
+
PRINTK_2(TRACE_MWAVE,
"mwavedd::mwave_ioctl, thread for"
" ipc %x going to sleep\n",
ipcnum);
-
- spin_lock_irqsave(&ipc_lock, flags);
+ add_wait_queue(&pDrvData->IPCs[ipcnum].ipc_wait_queue, &wait);
+ pDrvData->IPCs[ipcnum].bIsHere = TRUE;
+ set_current_state(TASK_INTERRUPTIBLE);
/* check whether an event was signalled by */
/* the interrupt handler while we were gone */
if (pDrvData->IPCs[ipcnum].usIntCount == 1) { /* first int has occurred (race condition) */
pDrvData->IPCs[ipcnum].usIntCount = 2; /* first int has been handled */
- spin_unlock_irqrestore(&ipc_lock, flags);
PRINTK_2(TRACE_MWAVE,
"mwavedd::mwave_ioctl"
" IOCTL_MW_GET_IPC ipcnum %x"
" handling first int\n",
ipcnum);
} else { /* either 1st int has not yet occurred, or we have already handled the first int */
- pDrvData->IPCs[ipcnum].bIsHere = TRUE;
-#warning "Sleeping on spinlock"
- interruptible_sleep_on(&pDrvData->IPCs[ipcnum].ipc_wait_queue);
- pDrvData->IPCs[ipcnum].bIsHere = FALSE;
+ schedule();
if (pDrvData->IPCs[ipcnum].usIntCount == 1) {
- pDrvData->IPCs[ipcnum].
- usIntCount = 2;
+ pDrvData->IPCs[ipcnum].usIntCount = 2;
}
- spin_unlock_irqrestore(&ipc_lock, flags);
PRINTK_2(TRACE_MWAVE,
"mwavedd::mwave_ioctl"
" IOCTL_MW_GET_IPC ipcnum %x"
@@ -343,6 +338,9 @@
" application\n",
ipcnum);
}
+ pDrvData->IPCs[ipcnum].bIsHere = FALSE;
+ remove_wait_queue(&pDrvData->IPCs[ipcnum].ipc_wait_queue, &wait);
+ set_current_state(TASK_RUNNING);
PRINTK_2(TRACE_MWAVE,
"mwavedd::mwave_ioctl IOCTL_MW_GET_IPC,"
" returning thread for ipc %x"
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