[PATCH] rcu-tasks: Fix race in schedule and flush work

Tue Feb 22 16:52:23 PST 2022

On Tue, Feb 22, 2022 at 11:06:29PM +0100, Padmanabha Srinivasaiah wrote:
> On Sun, Feb 20, 2022 at 12:04:25PM -0800, Paul E. McKenney wrote:
> > On Sun, Feb 20, 2022 at 07:35:17PM +0100, Padmanabha Srinivasaiah wrote:
> > > On Thu, Feb 17, 2022 at 09:43:30AM -0800, Paul E. McKenney wrote:
> > > > On Thu, Feb 17, 2022 at 04:25:19PM +0100, Padmanabha Srinivasaiah wrote:
> > > > > While booting secondary CPUs, cpus_read_[lock/unlock] not keeping online
> > > > > cpumask stable. The transient online mask results in below calltrace.
> > > > > 
> > > > > [    0.324121] CPU1: Booted secondary processor 0x0000000001 [0x410fd083]
> > > > > [    0.346652] Detected PIPT I-cache on CPU2
> > > > > [    0.347212] CPU2: Booted secondary processor 0x0000000002 [0x410fd083]
> > > > > [    0.377255] Detected PIPT I-cache on CPU3
> > > > > [    0.377823] CPU3: Booted secondary processor 0x0000000003 [0x410fd083]
> > > > > [    0.379040] ------------[ cut here ]------------
> > > > > [    0.383662] WARNING: CPU: 0 PID: 10 at kernel/workqueue.c:3084 __flush_work+0x12c/0x138
> > > > > [    0.384850] Modules linked in:
> > > > > [    0.385403] CPU: 0 PID: 10 Comm: rcu_tasks_rude_ Not tainted 5.17.0-rc3-v8+ #13
> > > > > [    0.386473] Hardware name: Raspberry Pi 4 Model B Rev 1.4 (DT)
> > > > > [    0.387289] pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > > > > [    0.388308] pc : __flush_work+0x12c/0x138
> > > > > [    0.388970] lr : __flush_work+0x80/0x138
> > > > > [    0.389620] sp : ffffffc00aaf3c60
> > > > > [    0.390139] x29: ffffffc00aaf3d20 x28: ffffffc009c16af0 x27: ffffff80f761df48
> > > > > [    0.391316] x26: 0000000000000004 x25: 0000000000000003 x24: 0000000000000100
> > > > > [    0.392493] x23: ffffffffffffffff x22: ffffffc009c16b10 x21: ffffffc009c16b28
> > > > > [    0.393668] x20: ffffffc009e53861 x19: ffffff80f77fbf40 x18: 00000000d744fcc9
> > > > > [    0.394842] x17: 000000000000000b x16: 00000000000001c2 x15: ffffffc009e57550
> > > > > [    0.396016] x14: 0000000000000000 x13: ffffffffffffffff x12: 0000000100000000
> > > > > [    0.397190] x11: 0000000000000462 x10: ffffff8040258008 x9 : 0000000100000000
> > > > > [    0.398364] x8 : 0000000000000000 x7 : ffffffc0093c8bf4 x6 : 0000000000000000
> > > > > [    0.399538] x5 : 0000000000000000 x4 : ffffffc00a976e40 x3 : ffffffc00810444c
> > > > > [    0.400711] x2 : 0000000000000004 x1 : 0000000000000000 x0 : 0000000000000000
> > > > > [    0.401886] Call trace:
> > > > > [    0.402309]  __flush_work+0x12c/0x138
> > > > > [    0.402941]  schedule_on_each_cpu+0x228/0x278
> > > > > [    0.403693]  rcu_tasks_rude_wait_gp+0x130/0x144
> > > > > [    0.404502]  rcu_tasks_kthread+0x220/0x254
> > > > > [    0.405264]  kthread+0x174/0x1ac
> > > > > [    0.405837]  ret_from_fork+0x10/0x20
> > > > > [    0.406456] irq event stamp: 102
> > > > > [    0.406966] hardirqs last  enabled at (101): [<ffffffc0093c8468>] _raw_spin_unlock_irq+0x78/0xb4
> > > > > [    0.408304] hardirqs last disabled at (102): [<ffffffc0093b8270>] el1_dbg+0x24/0x5c
> > > > > [    0.409410] softirqs last  enabled at (54): [<ffffffc0081b80c8>] local_bh_enable+0xc/0x2c
> > > > > [    0.410645] softirqs last disabled at (50): [<ffffffc0081b809c>] local_bh_disable+0xc/0x2c
> > > > > [    0.411890] ---[ end trace 0000000000000000 ]---
> > > > > [    0.413000] smp: Brought up 1 node, 4 CPUs
> > > > > [    0.413762] SMP: Total of 4 processors activated.
> > > > > [    0.414566] CPU features: detected: 32-bit EL0 Support
> > > > > [    0.415414] CPU features: detected: 32-bit EL1 Support
> > > > > [    0.416278] CPU features: detected: CRC32 instructions
> > > > > [    0.447021] Callback from call_rcu_tasks_rude() invoked.
> > > > > [    0.506693] Callback from call_rcu_tasks() invoked.
> > > > > 
> > > > > Link: https://lore.kernel.org/lkml/20220210184319.25009-1-treasure4paddy@gmail.com/T/
> > > > > Suggested-by: Paul E. McKenney <paulmck at kernel.org>
> > > > > Signed-off-by: Padmanabha Srinivasaiah <treasure4paddy at gmail.com>
> > > > 
> > > > Thank you, Padmanabha!  I have queued this with additional explanation
> > > > in the commit log as shown below.
> > > 
> > > Thanks paul.
> > > > 
> > > > If you have not already tested this by repeatedly rebooting, for
> > > > example continuously in an overnight test, could you please do so?
> > > > (I am assuming that your system can do an automated reboot loop, so no,
> > > > I am not asking you to stay up all night!)
> > > > 
> > > Yes, tested and issue doesn't appear.
> > 
> > Very good, thank you!
> > 
> > May I add your Tested-by?
> > 
> > 							Thanx, Paul
> >
> Sure paul. Once again thanks for the suggestion.
> 
> Tested-by: Padmanabha Srinivasaiah <treasure4paddy at gmail.com>

Thank you!  I will apply this on the next rebase.

							Thanx, Paul