lkml.org 
[lkml]   [2004]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[patch 1/1] uml:fix ubd deadlock on SMP
From
Date

Trivial: don't lock the queue spinlock when called from the request function.
Since the faulty function must use spinlock in another case, double-case it.
And since we will never use both functions together, let no object code be
shared between them.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
---

uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c | 36 ++++++++++++++++-----
1 files changed, 28 insertions(+), 8 deletions(-)

diff -puN arch/um/drivers/ubd_kern.c~uml-fix-ubd-deadlock arch/um/drivers/ubd_kern.c
--- uml-linux-2.6.8.1/arch/um/drivers/ubd_kern.c~uml-fix-ubd-deadlock 2004-09-08 19:04:27.662926344 +0200
+++ uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c 2004-09-08 19:05:36.700431048 +0200
@@ -54,6 +54,7 @@
#include "mem.h"
#include "mem_kern.h"

+/*This is the queue lock. FIXME: make it per-UBD device.*/
static spinlock_t ubd_io_lock = SPIN_LOCK_UNLOCKED;
static spinlock_t ubd_lock = SPIN_LOCK_UNLOCKED;

@@ -396,14 +397,16 @@ int thread_fd = -1;
*/
int intr_count = 0;

-static void ubd_finish(struct request *req, int error)
+static inline void __ubd_finish(struct request *req, int error, int lock)
{
int nsect;

if(error){
- spin_lock(&ubd_io_lock);
+ if (lock)
+ spin_lock(&ubd_io_lock);
end_request(req, 0);
- spin_unlock(&ubd_io_lock);
+ if (lock)
+ spin_unlock(&ubd_io_lock);
return;
}
nsect = req->current_nr_sectors;
@@ -412,11 +415,28 @@ static void ubd_finish(struct request *r
req->errors = 0;
req->nr_sectors -= nsect;
req->current_nr_sectors = 0;
- spin_lock(&ubd_io_lock);
+ if (lock)
+ spin_lock(&ubd_io_lock);
end_request(req, 1);
- spin_unlock(&ubd_io_lock);
+ if (lock)
+ spin_unlock(&ubd_io_lock);
+}
+
+/* We will use only one of them, not both, i.e. ubd_finish with the io_thread
+ * and ubd_finish_nolock without the separate io thread, so it's better to waste
+ * some space to gain performance. */
+
+static void ubd_finish(struct request *req, int error)
+{
+ __ubd_finish(req, error, 1);
+}
+
+static void ubd_finish_nolock(struct request *req, int error)
+{
+ __ubd_finish(req, error, 0);
}

+/*Called with ubd_io_lock not held*/
static void ubd_handler(void)
{
struct io_thread_req req;
@@ -965,6 +985,7 @@ static int prepare_mmap_request(struct u
return(0);
}

+/*Called with ubd_io_lock held*/
static int prepare_request(struct request *req, struct io_thread_req *io_req)
{
struct gendisk *disk = req->rq_disk;
@@ -977,9 +998,7 @@ static int prepare_request(struct reques
if((rq_data_dir(req) == WRITE) && !dev->openflags.w){
printk("Write attempted on readonly ubd device %s\n",
disk->disk_name);
- spin_lock(&ubd_io_lock);
end_request(req, 0);
- spin_unlock(&ubd_io_lock);
return(1);
}

@@ -1029,6 +1048,7 @@ static int prepare_request(struct reques
return(0);
}

+/*Called with ubd_io_lock held*/
static void do_ubd_request(request_queue_t *q)
{
struct io_thread_req io_req;
@@ -1040,7 +1060,7 @@ static void do_ubd_request(request_queue
err = prepare_request(req, &io_req);
if(!err){
do_io(&io_req);
- ubd_finish(req, io_req.error);
+ ubd_finish_nolock(req, io_req.error);
}
}
}
_
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2005-03-22 14:06    [W:0.063 / U:0.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site