diff options
| author | Jörn Engel <joern@logfs.org> | 2012-04-12 17:33:58 -0400 |
|---|---|---|
| committer | James Bottomley <JBottomley@Parallels.com> | 2012-05-17 10:08:54 +0100 |
| commit | 6acddc5e911bb3a4a007448371ed7317c85669da (patch) | |
| tree | ef5ac2ea141645723d2e898f83ed4414dc36f4bc /drivers/scsi/sg.c | |
| parent | ebaf466be5afa6c6dca29005374de4534e0e6b33 (diff) | |
[SCSI] sg: prevent unwoken sleep
srp->done is protected by sfp->rq_list_lock everywhere, except for this
one case. Result can be that the wake-up happens before the cacheline
with the changed srp->done has arrived, so the waiter can go back to
sleep and never be woken up again.
The wait_event_interruptible() means that anyone trying to debug this
unlikely race will likely notice everything working fine again, as the
next signal will unwedge things. Evil.
Signed-off-by: Joern Engel <joern@logfs.org>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Diffstat (limited to 'drivers/scsi/sg.c')
| -rw-r--r-- | drivers/scsi/sg.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 511e3ca1afd6..4a00364445f0 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -137,7 +137,8 @@ typedef struct sg_request { /* SG_MAX_QUEUE requests outstanding per file */ char res_used; /* 1 -> using reserve buffer, 0 -> not ... */ char orphan; /* 1 -> drop on sight, 0 -> normal */ char sg_io_owned; /* 1 -> packet belongs to SG_IO */ - volatile char done; /* 0->before bh, 1->before read, 2->read */ + /* done protected by rq_list_lock */ + char done; /* 0->before bh, 1->before read, 2->read */ struct request *rq; struct bio *bio; struct execute_work ew; @@ -760,6 +761,17 @@ sg_common_write(Sg_fd * sfp, Sg_request * srp, return 0; } +static int srp_done(Sg_fd *sfp, Sg_request *srp) +{ + unsigned long flags; + int ret; + + read_lock_irqsave(&sfp->rq_list_lock, flags); + ret = srp->done; + read_unlock_irqrestore(&sfp->rq_list_lock, flags); + return ret; +} + static int sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) { @@ -791,7 +803,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) if (result < 0) return result; result = wait_event_interruptible(sfp->read_wait, - (srp->done || sdp->detached)); + (srp_done(sfp, srp) || sdp->detached)); if (sdp->detached) return -ENODEV; write_lock_irq(&sfp->rq_list_lock); |