[+cc Guenter, linux-scsi] On Tue, Nov 11, 2014 at 4:33 PM, Barto <mister.freeman@xxxxxxxxxxx> wrote: > Hello everyone, > > I notice a bug since kernel 3.17 ( and also with 3.18 branch ), a random > hang at boot on some PC configurations, I did a "git bisect" and I found > that the culprit is : > > [045065d8a300a37218c548e9aa7becd581c6a0e8] [SCSI] fix qemu boot hang problem > > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=045065d8a300a37218c548e9aa7becd581c6a0e8 > > the author of this commit has choosen to inverse the logic of the if > statement in the file drivers/scsi/scsi_lib.c in order to solve an > issue with qemu : > > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -1774,7 +1774,7 @@ static void scsi_request_fn(struct request_queue *q) > blk_requeue_request(q, req); > atomic_dec(&sdev->device_busy); > out_delay: > - if (atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev)) > + if (!atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev)) > blk_delay_queue(q, SCSI_QUEUE_DELAY); > } > > this change triggers a bug on my PC ( I don't have SCSI devices, but > only 3 SATA harddisks and 2 IDE harddisks, SATA disks are on an ICH7 > sata controler on the motherboard gigabyte GA-P31-DS3L, and IDE disk on > a JMicron JMB363/368 Sata/IDE PCIe card ), every 5~10 boots the boot > stops suddenly because of this commit, > > If I revert this commit then the bug is gone, more details can be found > here, where I created a patch who reverts commit 045065d8 : > > https://bugzilla.kernel.org/show_bug.cgi?id=87581 > > my question: why Guenter Roeck ( the author of the bad commit ) has > choosen to inverse the logic in the if statement ? > before his commit the if statement was like this : > > if (atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev)) > blk_delay_queue(q, SCSI_QUEUE_DELAY); > > if his decision to inverse the logic of > "atomic_read(&sdev->device_busy)" is acceptable then the real bug is > probably located elsewhere in the scsi source code, and we must solve > this mistery because there is obviously a bug regression in SCSI code > because with older kernels ( 3.16.7 and lower ) I don't have the random > hang boot bug with my configuration, > > another user in archlinux forums has also this bug and he has a more > modern PC ( intel i7 core cpu, SSD device ), my fear is when linux > distros will move to kernel 3.17 then more users will have this weird > random bug who can occur only on boot and only with a specific PC > configuration, if the boot step is passed despite the random bug then > the bug will not occur, it occurs only during the boot process, which > probably means that the faulty source code is only called during the > boot process, > > thanks for anyone who wants to dig this problem with me > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
