From edce5e6f33a365c879b453286191bf397cc5efb4 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Mon, 7 Sep 2015 09:21:24 +0200 Subject: 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 [] 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] [] dump_stack+0x4c/0x65 [ 5174.890938] [] warn_slowpath_common+0x86/0xc0 [ 5174.891388] [] warn_slowpath_fmt+0x46/0x50 [ 5174.891808] [] ? uio_read+0x91/0x170 [uio] [ 5174.892237] [] ? uio_read+0x91/0x170 [uio] [ 5174.892653] [] __might_sleep+0x7d/0x90 [ 5174.893055] [] __might_fault+0x43/0xa0 [ 5174.893448] [] ? schedule+0x3e/0x90 [ 5174.893820] [] uio_read+0x132/0x170 [uio] [ 5174.894240] [] ? wake_up_q+0x70/0x70 [ 5174.894620] [] __vfs_read+0x28/0xe0 [ 5174.894993] [] ? security_file_permission+0xa3/0xc0 [ 5174.895541] [] ? rw_verify_area+0x4f/0xf0 [ 5174.896006] [] vfs_read+0x8a/0x140 [ 5174.896391] [] ? __schedule+0x425/0xcc0 [ 5174.896788] [] 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 Signed-off-by: Michal Hocko Signed-off-by: Greg Kroah-Hartman --- drivers/uio/uio.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/uio') diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index 8196581f54c2..bcc1fc027311 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 { -- cgit v1.2.3-70-g09d2