[PATCH v2] floppy: annotate data-races around command_status and floppy_work_fn
From: Cen Zhang
Date: Wed Mar 18 2026 - 00:05:38 EST
command_status is accessed by multiple contexts:
- generic_done() and do_wakeup() write it from the floppy
workqueue context.
- wait_til_done() reads it in wait_event conditions without
holding fdc_busy.
- is_alive() reads it locklessly to check driver liveness.
- floppy_queue_rq(), lock_fdc(), and unlock_fdc() write it
during FDC ownership transitions.
There is currently no LKMM annotation for these concurrent accesses
since command_status relies on the deprecated volatile qualifier.
Remove volatile and use READ_ONCE()/WRITE_ONCE() on every access
to command_status to provide proper LKMM data-race annotations.
Also annotate floppy_work_fn with WRITE_ONCE() in schedule_bh()
and READ_ONCE() in floppy_work_workfn(), and current_type[drive]
with READ_ONCE() in drive_no_geom() where it can be read without
holding the FDC lock.
The races were found by our tools:
1) command_status: generic_done (write) vs wait_til_done (read)
============ DATARACE ============
Function: generic_done+0x54/0xa0 drivers/block/floppy.c:985
Function: success_and_wakeup+0xeb/0x1e0 drivers/block/floppy.c:2046
Function: setup_rw_floppy+0x15dc/0x1d80 drivers/block/floppy.c:1046
Function: floppy_ready+0x2630/0x4000
Function: floppy_work_workfn+0x56/0x70 drivers/block/floppy.c:1012
Function: process_one_work kernel/workqueue.c:3236 [inline]
Function: process_scheduled_works+0x7a8/0x1030 kernel/workqueue.c:3319
============OTHER_INFO============
Function: wait_til_done+0x134/0x740 drivers/block/floppy.c:2026
Function: poll_drive+0x1fa/0x2a0
Function: fd_ioctl+0x13c8/0x1da0 drivers/block/floppy.c:3873
Function: blkdev_ioctl+0x421/0x510 block/ioctl.c:705
Function: vfs_ioctl fs/ioctl.c:51 [inline]
Function: __do_sys_ioctl fs/ioctl.c:598 [inline]
Function: __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
=================END==============
2) current_type[drive]: drive_no_geom (read) vs set_geometry (write)
============ DATARACE ============
Function: drive_no_geom drivers/block/floppy.c:606 [inline]
Function: floppy_check_events+0x9c9/0xcf0 drivers/block/floppy.c:4187
Function: disk_check_events+0xca/0x4d0 block/disk-events.c:193
Function: process_one_work kernel/workqueue.c:3236 [inline]
Function: process_scheduled_works+0x7a8/0x1030 kernel/workqueue.c:3319
Function: worker_thread+0xb97/0x11d0 kernel/workqueue.c:3400
Function: kthread+0x3d4/0x800 kernel/kthread.c:463
============OTHER_INFO============
Function: set_geometry+0xe1d/0x1980 drivers/block/floppy.c:2237
Function: fd_ioctl+0xff4/0x1da0 drivers/block/floppy.c:3912
Function: blkdev_ioctl+0x421/0x510 block/ioctl.c:705
Function: vfs_ioctl fs/ioctl.c:51 [inline]
Function: __do_sys_ioctl fs/ioctl.c:598 [inline]
Function: __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
=================END==============
3) floppy_work_fn: schedule_bh (write) vs
floppy_interrupt->schedule_bh (write)
============ DATARACE ============
Function: schedule_bh drivers/block/floppy.c:1005 [inline]
Function: do_wakeup+0x19c/0x220 drivers/block/floppy.c:3219
Function: success_and_wakeup+0x192/0x1e0 drivers/block/floppy.c:1994
Function: setup_rw_floppy+0x15dc/0x1d80 drivers/block/floppy.c:1046
Function: floppy_ready+0x2630/0x4000
Function: floppy_work_workfn+0x56/0x70 drivers/block/floppy.c:1012
Function: process_one_work kernel/workqueue.c:3236 [inline]
Function: process_scheduled_works+0x7a8/0x1030 kernel/workqueue.c:3319
============OTHER_INFO============
Function: floppy_interrupt+0xbf4/0x1220
Function: floppy_hardint+0x432/0x630
Function: __handle_irq_event_percpu+0x10a/0x5d0 kernel/irq/handle.c:158
Function: handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:210
Function: handle_edge_irq+0x223/0x9f0 kernel/irq/chip.c:855
=================END==============
Signed-off-by: Cen Zhang <zzzccc427@xxxxxxxxx>
---
drivers/block/floppy.c | 38 +++++++++++++++++++++-----------------
1 file changed, 21 insertions(+), 17 deletions(-)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 92e446a64371..cf8246e7155e 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -502,7 +502,7 @@ static int probing;
#define FD_COMMAND_ERROR 2
#define FD_COMMAND_OKAY 3
-static volatile int command_status = FD_COMMAND_NONE;
+static int command_status = FD_COMMAND_NONE;
static unsigned long fdc_busy;
static DECLARE_WAIT_QUEUE_HEAD(fdc_wait);
static DECLARE_WAIT_QUEUE_HEAD(command_done);
@@ -601,7 +601,8 @@ static inline void fdc_outb(unsigned char value, int fdc, int reg)
static inline bool drive_no_geom(int drive)
{
- return !current_type[drive] && !ITYPE(drive_state[drive].fd_device);
+ return !READ_ONCE(current_type[drive]) &&
+ !ITYPE(drive_state[drive].fd_device);
}
#ifndef fd_eject
@@ -640,7 +641,7 @@ static const char *timeout_message;
static void is_alive(const char *func, const char *message)
{
/* this routine checks whether the floppy driver is "alive" */
- if (test_bit(0, &fdc_busy) && command_status < 2 &&
+ if (test_bit(0, &fdc_busy) && READ_ONCE(command_status) < 2 &&
!delayed_work_pending(&fd_timeout)) {
DPRINT("%s: timeout handler died. %s\n", func, message);
}
@@ -892,7 +893,7 @@ static int lock_fdc(int drive)
if (wait_event_interruptible(fdc_wait, !test_and_set_bit(0, &fdc_busy)))
return -EINTR;
- command_status = FD_COMMAND_NONE;
+ WRITE_ONCE(command_status, FD_COMMAND_NONE);
reschedule_timeout(drive, "lock fdc");
set_fdc(drive);
@@ -906,7 +907,7 @@ static void unlock_fdc(void)
DPRINT("FDC access conflict!\n");
raw_cmd = NULL;
- command_status = FD_COMMAND_NONE;
+ WRITE_ONCE(command_status, FD_COMMAND_NONE);
cancel_delayed_work(&fd_timeout);
do_floppy = NULL;
cont = NULL;
@@ -990,7 +991,9 @@ static void (*floppy_work_fn)(void);
static void floppy_work_workfn(struct work_struct *work)
{
- floppy_work_fn();
+ void (*fn)(void) = READ_ONCE(floppy_work_fn);
+
+ fn();
}
static DECLARE_WORK(floppy_work, floppy_work_workfn);
@@ -999,7 +1002,7 @@ static void schedule_bh(void (*handler)(void))
{
WARN_ON(work_pending(&floppy_work));
- floppy_work_fn = handler;
+ WRITE_ONCE(floppy_work_fn, handler);
queue_work(floppy_wq, &floppy_work);
}
@@ -1864,7 +1867,7 @@ static void show_floppy(int fdc)
pr_info("cont=%p\n", cont);
pr_info("current_req=%p\n", current_req);
- pr_info("command_status=%d\n", command_status);
+ pr_info("command_status=%d\n", READ_ONCE(command_status));
pr_info("\n");
}
@@ -1991,7 +1994,7 @@ static void do_wakeup(void)
{
reschedule_timeout(MAXTIMEOUT, "do wakeup");
cont = NULL;
- command_status += 2;
+ WRITE_ONCE(command_status, READ_ONCE(command_status) + 2);
wake_up(&command_done);
}
@@ -2019,11 +2022,12 @@ static int wait_til_done(void (*handler)(void), bool interruptible)
schedule_bh(handler);
if (interruptible)
- wait_event_interruptible(command_done, command_status >= 2);
+ wait_event_interruptible(command_done,
+ READ_ONCE(command_status) >= 2);
else
- wait_event(command_done, command_status >= 2);
+ wait_event(command_done, READ_ONCE(command_status) >= 2);
- if (command_status < 2) {
+ if (READ_ONCE(command_status) < 2) {
cancel_activity();
cont = &intr_cont;
reset_fdc();
@@ -2031,18 +2035,18 @@ static int wait_til_done(void (*handler)(void), bool interruptible)
}
if (fdc_state[current_fdc].reset)
- command_status = FD_COMMAND_ERROR;
- if (command_status == FD_COMMAND_OKAY)
+ WRITE_ONCE(command_status, FD_COMMAND_ERROR);
+ if (READ_ONCE(command_status) == FD_COMMAND_OKAY)
ret = 0;
else
ret = -EIO;
- command_status = FD_COMMAND_NONE;
+ WRITE_ONCE(command_status, FD_COMMAND_NONE);
return ret;
}
static void generic_done(int result)
{
- command_status = result;
+ WRITE_ONCE(command_status, result);
cont = &wakeup_cont;
}
@@ -2873,7 +2877,7 @@ static blk_status_t floppy_queue_rq(struct blk_mq_hw_ctx *hctx,
list_add_tail(&bd->rq->queuelist, &floppy_reqs);
spin_unlock_irq(&floppy_lock);
- command_status = FD_COMMAND_NONE;
+ WRITE_ONCE(command_status, FD_COMMAND_NONE);
__reschedule_timeout(MAXTIMEOUT, "fd_request");
set_fdc(0);
process_fd_request();
--
2.34.1