* __might_sleep in uio_read()? @ 2015-09-02 22:45 Andy Grover 2015-09-02 23:11 ` Greg KH 2015-09-03 12:26 ` Michal Hocko 0 siblings, 2 replies; 8+ messages in thread From: Andy Grover @ 2015-09-02 22:45 UTC (permalink / raw) To: hjk, Greg KH; +Cc: linux-kernel Hi Hans and Greg, Is this an issue with uio? I swear it didn't used to throw this warning... Thanks -- Andy [ 5174.883261] ------------[ cut here ]------------ [ 5174.883617] WARNING: CPU: 0 PID: 1532 at /home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() [ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] [ 5174.885198] Modules linked in: tcm_loop target_core_user uio target_core_pscsi target_core_file target_core_iblock iscsi_target_mod target_core_mod uinput fuse nfsv3 nfs_acl nfs lockd grace fscache sunrpc microcode i2c_piix4 virtio_balloon i2c_core xfs libcrc32c crc32c_intel virtio_net virtio_blk [ 5174.887351] CPU: 0 PID: 1532 Comm: tcmu-runner Not tainted 4.2.0-rc7+ #178 [ 5174.887853] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014 [ 5174.888633] ffffffff81a3b870 ffff880045393ca8 ffffffff817afaae 0000000000000000 [ 5174.889224] ffff880045393cf8 ffff880045393ce8 ffffffff8109a846 ffff880045393cd8 [ 5174.889793] ffffffffa02a7150 00000000000002dc 0000000000000000 ffff880045008000 [ 5174.890375] Call Trace: [ 5174.890562] [<ffffffff817afaae>] dump_stack+0x4c/0x65 [ 5174.890938] [<ffffffff8109a846>] warn_slowpath_common+0x86/0xc0 [ 5174.891388] [<ffffffff8109a8c6>] warn_slowpath_fmt+0x46/0x50 [ 5174.891808] [<ffffffffa02a5821>] ? uio_read+0x91/0x170 [uio] [ 5174.892237] [<ffffffffa02a5821>] ? uio_read+0x91/0x170 [uio] [ 5174.892653] [<ffffffff810c584d>] __might_sleep+0x7d/0x90 [ 5174.893055] [<ffffffff811ea023>] __might_fault+0x43/0xa0 [ 5174.893448] [<ffffffff817b31ce>] ? schedule+0x3e/0x90 [ 5174.893820] [<ffffffffa02a58c2>] uio_read+0x132/0x170 [uio] [ 5174.894240] [<ffffffff810cbb80>] ? wake_up_q+0x70/0x70 [ 5174.894620] [<ffffffff81236168>] __vfs_read+0x28/0xe0 [ 5174.894993] [<ffffffff81353233>] ? security_file_permission+0xa3/0xc0 [ 5174.895541] [<ffffffff8123678f>] ? rw_verify_area+0x4f/0xf0 [ 5174.896006] [<ffffffff812368ba>] vfs_read+0x8a/0x140 [ 5174.896391] [<ffffffff817b28f5>] ? __schedule+0x425/0xcc0 [ 5174.896788] [<ffffffff812375d9>] SyS_read+0x49/0xb0 [ 5174.897160] [<ffffffff817b9bee>] entry_SYSCALL_64_fastpath+0x12/0x76 [ 5174.897625] ---[ end trace 61765cb39fe48dd5 ]--- ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: __might_sleep in uio_read()? 2015-09-02 22:45 __might_sleep in uio_read()? Andy Grover @ 2015-09-02 23:11 ` Greg KH 2015-09-03 12:26 ` Michal Hocko 1 sibling, 0 replies; 8+ messages in thread From: Greg KH @ 2015-09-02 23:11 UTC (permalink / raw) To: Andy Grover; +Cc: hjk, linux-kernel On Wed, Sep 02, 2015 at 03:45:10PM -0700, Andy Grover wrote: > Hi Hans and Greg, > > Is this an issue with uio? I swear it didn't used to throw this warning... > > Thanks -- Andy > > [ 5174.883261] ------------[ cut here ]------------ > [ 5174.883617] WARNING: CPU: 0 PID: 1532 at > /home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() > [ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at > [<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] > [ 5174.885198] Modules linked in: tcm_loop target_core_user uio > target_core_pscsi target_core_file target_core_iblock iscsi_target_mod > target_core_mod uinput fuse nfsv3 nfs_acl nfs lockd grace fscache sunrpc > microcode i2c_piix4 virtio_balloon i2c_core xfs libcrc32c crc32c_intel > virtio_net virtio_blk > [ 5174.887351] CPU: 0 PID: 1532 Comm: tcmu-runner Not tainted 4.2.0-rc7+ > #178 > [ 5174.887853] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > 1.8.1-20150318_183358- 04/01/2014 > [ 5174.888633] ffffffff81a3b870 ffff880045393ca8 ffffffff817afaae > 0000000000000000 > [ 5174.889224] ffff880045393cf8 ffff880045393ce8 ffffffff8109a846 > ffff880045393cd8 > [ 5174.889793] ffffffffa02a7150 00000000000002dc 0000000000000000 > ffff880045008000 > [ 5174.890375] Call Trace: > [ 5174.890562] [<ffffffff817afaae>] dump_stack+0x4c/0x65 > [ 5174.890938] [<ffffffff8109a846>] warn_slowpath_common+0x86/0xc0 > [ 5174.891388] [<ffffffff8109a8c6>] warn_slowpath_fmt+0x46/0x50 > [ 5174.891808] [<ffffffffa02a5821>] ? uio_read+0x91/0x170 [uio] > [ 5174.892237] [<ffffffffa02a5821>] ? uio_read+0x91/0x170 [uio] > [ 5174.892653] [<ffffffff810c584d>] __might_sleep+0x7d/0x90 > [ 5174.893055] [<ffffffff811ea023>] __might_fault+0x43/0xa0 > [ 5174.893448] [<ffffffff817b31ce>] ? schedule+0x3e/0x90 > [ 5174.893820] [<ffffffffa02a58c2>] uio_read+0x132/0x170 [uio] > [ 5174.894240] [<ffffffff810cbb80>] ? wake_up_q+0x70/0x70 > [ 5174.894620] [<ffffffff81236168>] __vfs_read+0x28/0xe0 > [ 5174.894993] [<ffffffff81353233>] ? security_file_permission+0xa3/0xc0 > [ 5174.895541] [<ffffffff8123678f>] ? rw_verify_area+0x4f/0xf0 > [ 5174.896006] [<ffffffff812368ba>] vfs_read+0x8a/0x140 > [ 5174.896391] [<ffffffff817b28f5>] ? __schedule+0x425/0xcc0 > [ 5174.896788] [<ffffffff812375d9>] SyS_read+0x49/0xb0 > [ 5174.897160] [<ffffffff817b9bee>] entry_SYSCALL_64_fastpath+0x12/0x76 > [ 5174.897625] ---[ end trace 61765cb39fe48dd5 ]--- I don't think anything has changed here in a while, any chance you can bisect this? And what uio driver are you using? thanks, greg k-h ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: __might_sleep in uio_read()? 2015-09-02 22:45 __might_sleep in uio_read()? Andy Grover 2015-09-02 23:11 ` Greg KH @ 2015-09-03 12:26 ` Michal Hocko 2015-09-03 18:47 ` Andy Grover 1 sibling, 1 reply; 8+ messages in thread From: Michal Hocko @ 2015-09-03 12:26 UTC (permalink / raw) To: Andy Grover; +Cc: hjk, Greg KH, linux-kernel On Wed 02-09-15 15:45:10, Andy Grover wrote: > Hi Hans and Greg, > > Is this an issue with uio? I swear it didn't used to throw this warning... > > Thanks -- Andy > > [ 5174.883261] ------------[ cut here ]------------ > [ 5174.883617] WARNING: CPU: 0 PID: 1532 at > /home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() > [ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at > [<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] The warning says that the driver is calling copy_to_user with TASK_INTERRUPTIBLE which is wrong in general because this context can sleep and a schedule would destroy the state. It doesn't matter here because the code would break out from the loop regardless of the copy_to_user return value. I assume that TASK_INTERRUPTIBLE is necessary before the event_count check to prevent from wake up races. If that is the case then you can simply do: diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index 3257d4220d01..7d8959e3833b 100644 --- a/drivers/uio/uio.c +++ b/drivers/uio/uio.c @@ -524,6 +524,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf, event_count = atomic_read(&idev->event); if (event_count != listener->event_count) { + __set_current_state(TASK_RUNNING); if (copy_to_user(buf, &event_count, count)) retval = -EFAULT; else { -- Michal Hocko SUSE Labs ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: __might_sleep in uio_read()? 2015-09-03 12:26 ` Michal Hocko @ 2015-09-03 18:47 ` Andy Grover 2015-09-03 19:12 ` Greg KH 2015-09-04 8:13 ` Michal Hocko 0 siblings, 2 replies; 8+ messages in thread From: Andy Grover @ 2015-09-03 18:47 UTC (permalink / raw) To: Michal Hocko; +Cc: hjk, Greg KH, linux-kernel On 09/03/2015 05:26 AM, Michal Hocko wrote: > On Wed 02-09-15 15:45:10, Andy Grover wrote: >> Hi Hans and Greg, >> >> Is this an issue with uio? I swear it didn't used to throw this warning... >> >> Thanks -- Andy >> >> [ 5174.883261] ------------[ cut here ]------------ >> [ 5174.883617] WARNING: CPU: 0 PID: 1532 at >> /home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() >> [ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at >> [<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] > > The warning says that the driver is calling copy_to_user with > TASK_INTERRUPTIBLE which is wrong in general because this context can > sleep and a schedule would destroy the state. It doesn't matter here > because the code would break out from the loop regardless of the > copy_to_user return value. > > I assume that TASK_INTERRUPTIBLE is necessary before the event_count > check to prevent from wake up races. If that is the case then you can > simply do: > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c > index 3257d4220d01..7d8959e3833b 100644 > --- a/drivers/uio/uio.c > +++ b/drivers/uio/uio.c > @@ -524,6 +524,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf, > > event_count = atomic_read(&idev->event); > if (event_count != listener->event_count) { > + __set_current_state(TASK_RUNNING); > if (copy_to_user(buf, &event_count, count)) > retval = -EFAULT; > else { > This certainly makes the warning go away. If this looks good to everyone else can we get this change in? Thanks -- Andy ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: __might_sleep in uio_read()? 2015-09-03 18:47 ` Andy Grover @ 2015-09-03 19:12 ` Greg KH 2015-09-03 20:12 ` Andy Grover 2015-09-04 8:13 ` Michal Hocko 1 sibling, 1 reply; 8+ messages in thread From: Greg KH @ 2015-09-03 19:12 UTC (permalink / raw) To: Andy Grover; +Cc: Michal Hocko, hjk, linux-kernel On Thu, Sep 03, 2015 at 11:47:34AM -0700, Andy Grover wrote: > On 09/03/2015 05:26 AM, Michal Hocko wrote: > >On Wed 02-09-15 15:45:10, Andy Grover wrote: > >>Hi Hans and Greg, > >> > >>Is this an issue with uio? I swear it didn't used to throw this warning... > >> > >>Thanks -- Andy > >> > >>[ 5174.883261] ------------[ cut here ]------------ > >>[ 5174.883617] WARNING: CPU: 0 PID: 1532 at > >>/home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() > >>[ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at > >>[<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] > > > >The warning says that the driver is calling copy_to_user with > >TASK_INTERRUPTIBLE which is wrong in general because this context can > >sleep and a schedule would destroy the state. It doesn't matter here > >because the code would break out from the loop regardless of the > >copy_to_user return value. > > > >I assume that TASK_INTERRUPTIBLE is necessary before the event_count > >check to prevent from wake up races. If that is the case then you can > >simply do: > >diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c > >index 3257d4220d01..7d8959e3833b 100644 > >--- a/drivers/uio/uio.c > >+++ b/drivers/uio/uio.c > >@@ -524,6 +524,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf, > > > > event_count = atomic_read(&idev->event); > > if (event_count != listener->event_count) { > >+ __set_current_state(TASK_RUNNING); > > if (copy_to_user(buf, &event_count, count)) > > retval = -EFAULT; > > else { > > > > This certainly makes the warning go away. If this looks good to everyone > else can we get this change in? What changed to require this? Why is this suddenly showing up now? thanks, greg k-h ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: __might_sleep in uio_read()? 2015-09-03 19:12 ` Greg KH @ 2015-09-03 20:12 ` Andy Grover 2015-09-04 3:59 ` Greg KH 0 siblings, 1 reply; 8+ messages in thread From: Andy Grover @ 2015-09-03 20:12 UTC (permalink / raw) To: Greg KH; +Cc: Michal Hocko, hjk, linux-kernel On 09/03/2015 12:12 PM, Greg KH wrote: > On Thu, Sep 03, 2015 at 11:47:34AM -0700, Andy Grover wrote: >> On 09/03/2015 05:26 AM, Michal Hocko wrote: >>> On Wed 02-09-15 15:45:10, Andy Grover wrote: >>>> Hi Hans and Greg, >>>> >>>> Is this an issue with uio? I swear it didn't used to throw this warning... >>>> >>>> Thanks -- Andy >>>> >>>> [ 5174.883261] ------------[ cut here ]------------ >>>> [ 5174.883617] WARNING: CPU: 0 PID: 1532 at >>>> /home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() >>>> [ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at >>>> [<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] >>> >>> The warning says that the driver is calling copy_to_user with >>> TASK_INTERRUPTIBLE which is wrong in general because this context can >>> sleep and a schedule would destroy the state. It doesn't matter here >>> because the code would break out from the loop regardless of the >>> copy_to_user return value. >>> >>> I assume that TASK_INTERRUPTIBLE is necessary before the event_count >>> check to prevent from wake up races. If that is the case then you can >>> simply do: >>> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c >>> index 3257d4220d01..7d8959e3833b 100644 >>> --- a/drivers/uio/uio.c >>> +++ b/drivers/uio/uio.c >>> @@ -524,6 +524,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf, >>> >>> event_count = atomic_read(&idev->event); >>> if (event_count != listener->event_count) { >>> + __set_current_state(TASK_RUNNING); >>> if (copy_to_user(buf, &event_count, count)) >>> retval = -EFAULT; >>> else { >>> >> >> This certainly makes the warning go away. If this looks good to everyone >> else can we get this change in? > > What changed to require this? Why is this suddenly showing up now? I'm working on drivers/target/target_core_user.c, a SCSI userspace passthrough that was added in 3.18, aka TCMU, which uses uio. The checks for !TASK_RUNNING were added in 3.19 (8eb23b9f3 and 00845eb96) ...and I'm just getting back to TCMU development after a bit, so maybe I'm the first one to call uio_read since those checks were added in 3.19? -- Andy ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: __might_sleep in uio_read()? 2015-09-03 20:12 ` Andy Grover @ 2015-09-04 3:59 ` Greg KH 0 siblings, 0 replies; 8+ messages in thread From: Greg KH @ 2015-09-04 3:59 UTC (permalink / raw) To: Andy Grover; +Cc: Michal Hocko, hjk, linux-kernel On Thu, Sep 03, 2015 at 01:12:28PM -0700, Andy Grover wrote: > On 09/03/2015 12:12 PM, Greg KH wrote: > >On Thu, Sep 03, 2015 at 11:47:34AM -0700, Andy Grover wrote: > >>On 09/03/2015 05:26 AM, Michal Hocko wrote: > >>>On Wed 02-09-15 15:45:10, Andy Grover wrote: > >>>>Hi Hans and Greg, > >>>> > >>>>Is this an issue with uio? I swear it didn't used to throw this warning... > >>>> > >>>>Thanks -- Andy > >>>> > >>>>[ 5174.883261] ------------[ cut here ]------------ > >>>>[ 5174.883617] WARNING: CPU: 0 PID: 1532 at > >>>>/home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() > >>>>[ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at > >>>>[<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] > >>> > >>>The warning says that the driver is calling copy_to_user with > >>>TASK_INTERRUPTIBLE which is wrong in general because this context can > >>>sleep and a schedule would destroy the state. It doesn't matter here > >>>because the code would break out from the loop regardless of the > >>>copy_to_user return value. > >>> > >>>I assume that TASK_INTERRUPTIBLE is necessary before the event_count > >>>check to prevent from wake up races. If that is the case then you can > >>>simply do: > >>>diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c > >>>index 3257d4220d01..7d8959e3833b 100644 > >>>--- a/drivers/uio/uio.c > >>>+++ b/drivers/uio/uio.c > >>>@@ -524,6 +524,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf, > >>> > >>> event_count = atomic_read(&idev->event); > >>> if (event_count != listener->event_count) { > >>>+ __set_current_state(TASK_RUNNING); > >>> if (copy_to_user(buf, &event_count, count)) > >>> retval = -EFAULT; > >>> else { > >>> > >> > >>This certainly makes the warning go away. If this looks good to everyone > >>else can we get this change in? > > > >What changed to require this? Why is this suddenly showing up now? > > I'm working on drivers/target/target_core_user.c, a SCSI userspace > passthrough that was added in 3.18, aka TCMU, which uses uio. > > The checks for !TASK_RUNNING were added in 3.19 (8eb23b9f3 and 00845eb96) > > ...and I'm just getting back to TCMU development after a bit, so maybe I'm > the first one to call uio_read since those checks were added in 3.19? If so, that's sad. greg k-h ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: __might_sleep in uio_read()? 2015-09-03 18:47 ` Andy Grover 2015-09-03 19:12 ` Greg KH @ 2015-09-04 8:13 ` Michal Hocko 1 sibling, 0 replies; 8+ messages in thread From: Michal Hocko @ 2015-09-04 8:13 UTC (permalink / raw) To: Andy Grover; +Cc: hjk, Greg KH, linux-kernel On Thu 03-09-15 11:47:34, Andy Grover wrote: > On 09/03/2015 05:26 AM, Michal Hocko wrote: > >On Wed 02-09-15 15:45:10, Andy Grover wrote: > >>Hi Hans and Greg, > >> > >>Is this an issue with uio? I swear it didn't used to throw this warning... > >> > >>Thanks -- Andy > >> > >>[ 5174.883261] ------------[ cut here ]------------ > >>[ 5174.883617] WARNING: CPU: 0 PID: 1532 at > >>/home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() > >>[ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at > >>[<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] > > > >The warning says that the driver is calling copy_to_user with > >TASK_INTERRUPTIBLE which is wrong in general because this context can > >sleep and a schedule would destroy the state. It doesn't matter here > >because the code would break out from the loop regardless of the > >copy_to_user return value. > > > >I assume that TASK_INTERRUPTIBLE is necessary before the event_count > >check to prevent from wake up races. If that is the case then you can > >simply do: > >diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c > >index 3257d4220d01..7d8959e3833b 100644 > >--- a/drivers/uio/uio.c > >+++ b/drivers/uio/uio.c > >@@ -524,6 +524,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf, > > > > event_count = atomic_read(&idev->event); > > if (event_count != listener->event_count) { > >+ __set_current_state(TASK_RUNNING); > > if (copy_to_user(buf, &event_count, count)) > > retval = -EFAULT; > > else { > > > > This certainly makes the warning go away. If this looks good to everyone > else can we get this change in? --- >From f50005095a90d21f628d8ce6525b432f17c8138c Mon Sep 17 00:00:00 2001 From: Michal Hocko <mhocko@suse.com> Date: Fri, 4 Sep 2015 10:08:18 +0200 Subject: [PATCH] uio: fix false positive __might_sleep warning splat Andy has reported a __might_sleep warning [ 5174.883617] WARNING: CPU: 0 PID: 1532 at /home/agrover/git/kernel/kernel/sched/core.c:7389 __might_sleep+0x7d/0x90() [ 5174.884407] do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffffa02a5821>] uio_read+0x91/0x170 [uio] [ 5174.885198] Modules linked in: tcm_loop target_core_user uio target_core_pscsi target_core_file target_core_iblock iscsi_target_mod target_core_mod uinput fuse nfsv3 nfs_acl nfs lockd grace fscache sunrpc microcode i2c_piix4 virtio_balloon i2c_core xfs libcrc32c crc32c_intel virtio_net virtio_blk [ 5174.887351] CPU: 0 PID: 1532 Comm: tcmu-runner Not tainted 4.2.0-rc7+ [ 5174.887853] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014 [ 5174.888633] ffffffff81a3b870 ffff880045393ca8 ffffffff817afaae 0000000000000000 [ 5174.889224] ffff880045393cf8 ffff880045393ce8 ffffffff8109a846 ffff880045393cd8 [ 5174.889793] ffffffffa02a7150 00000000000002dc 0000000000000000 ffff880045008000 [ 5174.890375] Call Trace: [ 5174.890562] [<ffffffff817afaae>] dump_stack+0x4c/0x65 [ 5174.890938] [<ffffffff8109a846>] warn_slowpath_common+0x86/0xc0 [ 5174.891388] [<ffffffff8109a8c6>] warn_slowpath_fmt+0x46/0x50 [ 5174.891808] [<ffffffffa02a5821>] ? uio_read+0x91/0x170 [uio] [ 5174.892237] [<ffffffffa02a5821>] ? uio_read+0x91/0x170 [uio] [ 5174.892653] [<ffffffff810c584d>] __might_sleep+0x7d/0x90 [ 5174.893055] [<ffffffff811ea023>] __might_fault+0x43/0xa0 [ 5174.893448] [<ffffffff817b31ce>] ? schedule+0x3e/0x90 [ 5174.893820] [<ffffffffa02a58c2>] uio_read+0x132/0x170 [uio] [ 5174.894240] [<ffffffff810cbb80>] ? wake_up_q+0x70/0x70 [ 5174.894620] [<ffffffff81236168>] __vfs_read+0x28/0xe0 [ 5174.894993] [<ffffffff81353233>] ? security_file_permission+0xa3/0xc0 [ 5174.895541] [<ffffffff8123678f>] ? rw_verify_area+0x4f/0xf0 [ 5174.896006] [<ffffffff812368ba>] vfs_read+0x8a/0x140 [ 5174.896391] [<ffffffff817b28f5>] ? __schedule+0x425/0xcc0 [ 5174.896788] [<ffffffff812375d9>] SyS_read+0x49/0xb0 The warning is a false positive because uio_read doesn't depent on TASK_INTERRUPTIBLE after copy_to_user so it is safe to silence the warning by an explicit setting the state to TASK_RUNNING in the path which might call into TASK_RUNNING. Reported-by: Andy Grover <agrover@redhat.com> Signed-off-by: Michal Hocko <mhocko@suse.com> --- drivers/uio/uio.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index 3257d4220d01..7d8959e3833b 100644 --- a/drivers/uio/uio.c +++ b/drivers/uio/uio.c @@ -524,6 +524,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf, event_count = atomic_read(&idev->event); if (event_count != listener->event_count) { + __set_current_state(TASK_RUNNING); if (copy_to_user(buf, &event_count, count)) retval = -EFAULT; else { -- 2.5.0 -- Michal Hocko SUSE Labs ^ permalink raw reply related [flat|nested] 8+ messages in thread
end of thread, other threads:[~2015-09-04 8:14 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-09-02 22:45 __might_sleep in uio_read()? Andy Grover 2015-09-02 23:11 ` Greg KH 2015-09-03 12:26 ` Michal Hocko 2015-09-03 18:47 ` Andy Grover 2015-09-03 19:12 ` Greg KH 2015-09-03 20:12 ` Andy Grover 2015-09-04 3:59 ` Greg KH 2015-09-04 8:13 ` Michal Hocko
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