From 6acddc5e911bb3a4a007448371ed7317c85669da Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rn=20Engel?= Date: Thu, 12 Apr 2012 17:33:58 -0400 Subject: [PATCH] [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 Acked-by: Douglas Gilbert Signed-off-by: James Bottomley --- drivers/scsi/sg.c | 16 ++++++++++++++-- 1 file 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);