Linux-ARM-Kernel Archive on lore.kernel.org
 help / color / Atom feed
* [PATCH] char/random: silence a lockdep splat with printk()
@ 2019-11-13 21:16 Qian Cai
  2019-12-03 18:46 ` Qian Cai
  0 siblings, 1 reply; 3+ messages in thread
From: Qian Cai @ 2019-11-13 21:16 UTC (permalink / raw)
  To: tytso
  Cc: pmladek, sergey.senozhatsky.work, arnd, peterz, catalin.marinas,
	linux-kernel, rostedt, linux-mm, Qian Cai, gregkh, longman,
	dan.j.williams, will, tglx, linux-arm-kernel

From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>

Sergey didn't like the locking order,

uart_port->lock  ->  tty_port->lock

uart_write (uart_port->lock)
  __uart_start
    pl011_start_tx
      pl011_tx_chars
        uart_write_wakeup
          tty_port_tty_wakeup
            tty_port_default
              tty_port_tty_get (tty_port->lock)

but those code is so old, and I have no clue how to de-couple it after
checking other locks in the splat. There is an onging effort to make all
printk() as deferred, so until that happens, workaround it for now as a
short-term fix.

LTP: starting iogen01 (export LTPROOT; rwtest -N iogen01 -i 120s -s
read,write -Da -Dv -n 2 500b:$TMPDIR/doio.f1.$$
1000b:$TMPDIR/doio.f2.$$)
WARNING: possible circular locking dependency detected
------------------------------------------------------
doio/49441 is trying to acquire lock:
ffff008b7cff7290 (&(&zone->lock)->rlock){..-.}, at: rmqueue+0x138/0x2050

but task is already holding lock:
60ff000822352818 (&pool->lock/1){-.-.}, at: start_flush_work+0xd8/0x3f0

  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:

  -> #4 (&pool->lock/1){-.-.}:
       lock_acquire+0x320/0x360
       _raw_spin_lock+0x64/0x80
       __queue_work+0x4b4/0xa10
       queue_work_on+0xac/0x11c
       tty_schedule_flip+0x84/0xbc
       tty_flip_buffer_push+0x1c/0x28
       pty_write+0x98/0xd0
       n_tty_write+0x450/0x60c
       tty_write+0x338/0x474
       __vfs_write+0x88/0x214
       vfs_write+0x12c/0x1a4
       redirected_tty_write+0x90/0xdc
       do_loop_readv_writev+0x140/0x180
       do_iter_write+0xe0/0x10c
       vfs_writev+0x134/0x1cc
       do_writev+0xbc/0x130
       __arm64_sys_writev+0x58/0x8c
       el0_svc_handler+0x170/0x240
       el0_sync_handler+0x150/0x250
       el0_sync+0x164/0x180

  -> #3 (&(&port->lock)->rlock){-.-.}:
       lock_acquire+0x320/0x360
       _raw_spin_lock_irqsave+0x7c/0x9c
       tty_port_tty_get+0x24/0x60
       tty_port_default_wakeup+0x1c/0x3c
       tty_port_tty_wakeup+0x34/0x40
       uart_write_wakeup+0x28/0x44
       pl011_tx_chars+0x1b8/0x270
       pl011_start_tx+0x24/0x70
       __uart_start+0x5c/0x68
       uart_write+0x164/0x1c8
       do_output_char+0x33c/0x348
       n_tty_write+0x4bc/0x60c
       tty_write+0x338/0x474
       redirected_tty_write+0xc0/0xdc
       do_loop_readv_writev+0x140/0x180
       do_iter_write+0xe0/0x10c
       vfs_writev+0x134/0x1cc
       do_writev+0xbc/0x130
       __arm64_sys_writev+0x58/0x8c
       el0_svc_handler+0x170/0x240
       el0_sync_handler+0x150/0x250
       el0_sync+0x164/0x180

  -> #2 (&port_lock_key){-.-.}:
       lock_acquire+0x320/0x360
       _raw_spin_lock+0x64/0x80
       pl011_console_write+0xec/0x2cc
       console_unlock+0x794/0x96c
       vprintk_emit+0x260/0x31c
       vprintk_default+0x54/0x7c
       vprintk_func+0x218/0x254
       printk+0x7c/0xa4
       register_console+0x734/0x7b0
       uart_add_one_port+0x734/0x834
       pl011_register_port+0x6c/0xac
       sbsa_uart_probe+0x234/0x2ec
       platform_drv_probe+0xd4/0x124
       really_probe+0x250/0x71c
       driver_probe_device+0xb4/0x200
       __device_attach_driver+0xd8/0x188
       bus_for_each_drv+0xbc/0x110
       __device_attach+0x120/0x220
       device_initial_probe+0x20/0x2c
       bus_probe_device+0x54/0x100
       device_add+0xae8/0xc2c
       platform_device_add+0x278/0x3b8
       platform_device_register_full+0x238/0x2ac
       acpi_create_platform_device+0x2dc/0x3a8
       acpi_bus_attach+0x390/0x3cc
       acpi_bus_attach+0x108/0x3cc
       acpi_bus_attach+0x108/0x3cc
       acpi_bus_attach+0x108/0x3cc
       acpi_bus_scan+0x7c/0xb0
       acpi_scan_init+0xe4/0x304
       acpi_init+0x100/0x114
       do_one_initcall+0x348/0x6a0
       do_initcall_level+0x190/0x1fc
       do_basic_setup+0x34/0x4c
       kernel_init_freeable+0x19c/0x260
       kernel_init+0x18/0x338
       ret_from_fork+0x10/0x18

  -> #1 (console_owner){-...}:
       lock_acquire+0x320/0x360
       console_lock_spinning_enable+0x6c/0x7c
       console_unlock+0x4f8/0x96c
       vprintk_emit+0x260/0x31c
       vprintk_default+0x54/0x7c
       vprintk_func+0x218/0x254
       printk+0x7c/0xa4
       get_random_u64+0x1c4/0x1dc
       shuffle_pick_tail+0x40/0xac
       __free_one_page+0x424/0x710
       free_one_page+0x70/0x120
       __free_pages_ok+0x61c/0xa94
       __free_pages_core+0x1bc/0x294
       memblock_free_pages+0x38/0x48
       __free_pages_memory+0xcc/0xfc
       __free_memory_core+0x70/0x78
       free_low_memory_core_early+0x148/0x18c
       memblock_free_all+0x18/0x54
       mem_init+0xb4/0x17c
       mm_init+0x14/0x38
       start_kernel+0x19c/0x530

  -> #0 (&(&zone->lock)->rlock){..-.}:
       validate_chain+0xf6c/0x2e2c
       __lock_acquire+0x868/0xc2c
       lock_acquire+0x320/0x360
       _raw_spin_lock+0x64/0x80
       rmqueue+0x138/0x2050
       get_page_from_freelist+0x474/0x688
       __alloc_pages_nodemask+0x3b4/0x18dc
       alloc_pages_current+0xd0/0xe0
       alloc_slab_page+0x2b4/0x5e0
       new_slab+0xc8/0x6bc
       ___slab_alloc+0x3b8/0x640
       kmem_cache_alloc+0x4b4/0x588
       __debug_object_init+0x778/0x8b4
       debug_object_init_on_stack+0x40/0x50
       start_flush_work+0x16c/0x3f0
       __flush_work+0xb8/0x124
       flush_work+0x20/0x30
       xlog_cil_force_lsn+0x88/0x204 [xfs]
       xfs_log_force_lsn+0x128/0x1b8 [xfs]
       xfs_file_fsync+0x3c4/0x488 [xfs]
       vfs_fsync_range+0xb0/0xd0
       generic_write_sync+0x80/0xa0 [xfs]
       xfs_file_buffered_aio_write+0x66c/0x6e4 [xfs]
       xfs_file_write_iter+0x1a0/0x218 [xfs]
       __vfs_write+0x1cc/0x214
       vfs_write+0x12c/0x1a4
       ksys_write+0xb0/0x120
       __arm64_sys_write+0x54/0x88
       el0_svc_handler+0x170/0x240
       el0_sync_handler+0x150/0x250
       el0_sync+0x164/0x180

       other info that might help us debug this:

 Chain exists of:
   &(&zone->lock)->rlock --> &(&port->lock)->rlock --> &pool->lock/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pool->lock/1);
                               lock(&(&port->lock)->rlock);
                               lock(&pool->lock/1);
  lock(&(&zone->lock)->rlock);

                *** DEADLOCK ***

4 locks held by doio/49441:
 #0: a0ff00886fc27408 (sb_writers#8){.+.+}, at: vfs_write+0x118/0x1a4
 #1: 8fff00080810dfe0 (&xfs_nondir_ilock_class){++++}, at:
xfs_ilock+0x2a8/0x300 [xfs]
 #2: ffff9000129f2390 (rcu_read_lock){....}, at:
rcu_lock_acquire+0x8/0x38
 #3: 60ff000822352818 (&pool->lock/1){-.-.}, at:
start_flush_work+0xd8/0x3f0

               stack backtrace:
CPU: 48 PID: 49441 Comm: doio Tainted: G        W
Hardware name: HPE Apollo 70             /C01_APACHE_MB         , BIOS
L50_5.13_1.11 06/18/2019
Call trace:
 dump_backtrace+0x0/0x248
 show_stack+0x20/0x2c
 dump_stack+0xe8/0x150
 print_circular_bug+0x368/0x380
 check_noncircular+0x28c/0x294
 validate_chain+0xf6c/0x2e2c
 __lock_acquire+0x868/0xc2c
 lock_acquire+0x320/0x360
 _raw_spin_lock+0x64/0x80
 rmqueue+0x138/0x2050
 get_page_from_freelist+0x474/0x688
 __alloc_pages_nodemask+0x3b4/0x18dc
 alloc_pages_current+0xd0/0xe0
 alloc_slab_page+0x2b4/0x5e0
 new_slab+0xc8/0x6bc
 ___slab_alloc+0x3b8/0x640
 kmem_cache_alloc+0x4b4/0x588
 __debug_object_init+0x778/0x8b4
 debug_object_init_on_stack+0x40/0x50
 start_flush_work+0x16c/0x3f0
 __flush_work+0xb8/0x124
 flush_work+0x20/0x30
 xlog_cil_force_lsn+0x88/0x204 [xfs]
 xfs_log_force_lsn+0x128/0x1b8 [xfs]
 xfs_file_fsync+0x3c4/0x488 [xfs]
 vfs_fsync_range+0xb0/0xd0
 generic_write_sync+0x80/0xa0 [xfs]
 xfs_file_buffered_aio_write+0x66c/0x6e4 [xfs]
 xfs_file_write_iter+0x1a0/0x218 [xfs]
 __vfs_write+0x1cc/0x214
 vfs_write+0x12c/0x1a4
 ksys_write+0xb0/0x120
 __arm64_sys_write+0x54/0x88
 el0_svc_handler+0x170/0x240
 el0_sync_handler+0x150/0x250
 el0_sync+0x164/0x180

[cai@lca.pw: add a commit log.]
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Qian Cai <cai@lca.pw>
---

Sergey, please let us know if you are fine with the Signed-off-by.

 drivers/char/random.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 46afd14facb7..b90086c9836f 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1688,8 +1688,9 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
 	print_once = true;
 #endif
 	if (__ratelimit(&unseeded_warning))
-		pr_notice("random: %s called from %pS with crng_init=%d\n",
-			  func_name, caller, crng_init);
+		printk_deferred(KERN_NOTICE "random: %s called from %pS "
+				"with crng_init=%d\n", func_name, caller,
+				crng_init);
 }
 
 /*
-- 
1.8.3.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] char/random: silence a lockdep splat with printk()
  2019-11-13 21:16 [PATCH] char/random: silence a lockdep splat with printk() Qian Cai
@ 2019-12-03 18:46 ` Qian Cai
  2019-12-05  1:00   ` Sergey Senozhatsky
  0 siblings, 1 reply; 3+ messages in thread
From: Qian Cai @ 2019-12-03 18:46 UTC (permalink / raw)
  To: tytso
  Cc: pmladek, sergey.senozhatsky.work, Arnd Bergmann, peterz,
	Catalin Marinas, linux-kernel, rostedt, linux-mm, gregkh,
	longman, dan.j.williams, will, tglx, linux-arm-kernel



> On Nov 13, 2019, at 4:16 PM, Qian Cai <cai@lca.pw> wrote:
> 
> From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> 
> Sergey didn't like the locking order,
> 
> uart_port->lock  ->  tty_port->lock
> 
> uart_write (uart_port->lock)
>  __uart_start
>    pl011_start_tx
>      pl011_tx_chars
>        uart_write_wakeup
>          tty_port_tty_wakeup
>            tty_port_default
>              tty_port_tty_get (tty_port->lock)
> 
> but those code is so old, and I have no clue how to de-couple it after
> checking other locks in the splat. There is an onging effort to make all
> printk() as deferred, so until that happens, workaround it for now as a
> short-term fix.

Sergey, could we have a ACK from you so Ted might be able to merge?

> 
> LTP: starting iogen01 (export LTPROOT; rwtest -N iogen01 -i 120s -s
> read,write -Da -Dv -n 2 500b:$TMPDIR/doio.f1.$$
> 1000b:$TMPDIR/doio.f2.$$)
> WARNING: possible circular locking dependency detected
> ------------------------------------------------------
> doio/49441 is trying to acquire lock:
> ffff008b7cff7290 (&(&zone->lock)->rlock){..-.}, at: rmqueue+0x138/0x2050
> 
> but task is already holding lock:
> 60ff000822352818 (&pool->lock/1){-.-.}, at: start_flush_work+0xd8/0x3f0
> 
>  which lock already depends on the new lock.
> 
>  the existing dependency chain (in reverse order) is:
> 
>  -> #4 (&pool->lock/1){-.-.}:
>       lock_acquire+0x320/0x360
>       _raw_spin_lock+0x64/0x80
>       __queue_work+0x4b4/0xa10
>       queue_work_on+0xac/0x11c
>       tty_schedule_flip+0x84/0xbc
>       tty_flip_buffer_push+0x1c/0x28
>       pty_write+0x98/0xd0
>       n_tty_write+0x450/0x60c
>       tty_write+0x338/0x474
>       __vfs_write+0x88/0x214
>       vfs_write+0x12c/0x1a4
>       redirected_tty_write+0x90/0xdc
>       do_loop_readv_writev+0x140/0x180
>       do_iter_write+0xe0/0x10c
>       vfs_writev+0x134/0x1cc
>       do_writev+0xbc/0x130
>       __arm64_sys_writev+0x58/0x8c
>       el0_svc_handler+0x170/0x240
>       el0_sync_handler+0x150/0x250
>       el0_sync+0x164/0x180
> 
>  -> #3 (&(&port->lock)->rlock){-.-.}:
>       lock_acquire+0x320/0x360
>       _raw_spin_lock_irqsave+0x7c/0x9c
>       tty_port_tty_get+0x24/0x60
>       tty_port_default_wakeup+0x1c/0x3c
>       tty_port_tty_wakeup+0x34/0x40
>       uart_write_wakeup+0x28/0x44
>       pl011_tx_chars+0x1b8/0x270
>       pl011_start_tx+0x24/0x70
>       __uart_start+0x5c/0x68
>       uart_write+0x164/0x1c8
>       do_output_char+0x33c/0x348
>       n_tty_write+0x4bc/0x60c
>       tty_write+0x338/0x474
>       redirected_tty_write+0xc0/0xdc
>       do_loop_readv_writev+0x140/0x180
>       do_iter_write+0xe0/0x10c
>       vfs_writev+0x134/0x1cc
>       do_writev+0xbc/0x130
>       __arm64_sys_writev+0x58/0x8c
>       el0_svc_handler+0x170/0x240
>       el0_sync_handler+0x150/0x250
>       el0_sync+0x164/0x180
> 
>  -> #2 (&port_lock_key){-.-.}:
>       lock_acquire+0x320/0x360
>       _raw_spin_lock+0x64/0x80
>       pl011_console_write+0xec/0x2cc
>       console_unlock+0x794/0x96c
>       vprintk_emit+0x260/0x31c
>       vprintk_default+0x54/0x7c
>       vprintk_func+0x218/0x254
>       printk+0x7c/0xa4
>       register_console+0x734/0x7b0
>       uart_add_one_port+0x734/0x834
>       pl011_register_port+0x6c/0xac
>       sbsa_uart_probe+0x234/0x2ec
>       platform_drv_probe+0xd4/0x124
>       really_probe+0x250/0x71c
>       driver_probe_device+0xb4/0x200
>       __device_attach_driver+0xd8/0x188
>       bus_for_each_drv+0xbc/0x110
>       __device_attach+0x120/0x220
>       device_initial_probe+0x20/0x2c
>       bus_probe_device+0x54/0x100
>       device_add+0xae8/0xc2c
>       platform_device_add+0x278/0x3b8
>       platform_device_register_full+0x238/0x2ac
>       acpi_create_platform_device+0x2dc/0x3a8
>       acpi_bus_attach+0x390/0x3cc
>       acpi_bus_attach+0x108/0x3cc
>       acpi_bus_attach+0x108/0x3cc
>       acpi_bus_attach+0x108/0x3cc
>       acpi_bus_scan+0x7c/0xb0
>       acpi_scan_init+0xe4/0x304
>       acpi_init+0x100/0x114
>       do_one_initcall+0x348/0x6a0
>       do_initcall_level+0x190/0x1fc
>       do_basic_setup+0x34/0x4c
>       kernel_init_freeable+0x19c/0x260
>       kernel_init+0x18/0x338
>       ret_from_fork+0x10/0x18
> 
>  -> #1 (console_owner){-...}:
>       lock_acquire+0x320/0x360
>       console_lock_spinning_enable+0x6c/0x7c
>       console_unlock+0x4f8/0x96c
>       vprintk_emit+0x260/0x31c
>       vprintk_default+0x54/0x7c
>       vprintk_func+0x218/0x254
>       printk+0x7c/0xa4
>       get_random_u64+0x1c4/0x1dc
>       shuffle_pick_tail+0x40/0xac
>       __free_one_page+0x424/0x710
>       free_one_page+0x70/0x120
>       __free_pages_ok+0x61c/0xa94
>       __free_pages_core+0x1bc/0x294
>       memblock_free_pages+0x38/0x48
>       __free_pages_memory+0xcc/0xfc
>       __free_memory_core+0x70/0x78
>       free_low_memory_core_early+0x148/0x18c
>       memblock_free_all+0x18/0x54
>       mem_init+0xb4/0x17c
>       mm_init+0x14/0x38
>       start_kernel+0x19c/0x530
> 
>  -> #0 (&(&zone->lock)->rlock){..-.}:
>       validate_chain+0xf6c/0x2e2c
>       __lock_acquire+0x868/0xc2c
>       lock_acquire+0x320/0x360
>       _raw_spin_lock+0x64/0x80
>       rmqueue+0x138/0x2050
>       get_page_from_freelist+0x474/0x688
>       __alloc_pages_nodemask+0x3b4/0x18dc
>       alloc_pages_current+0xd0/0xe0
>       alloc_slab_page+0x2b4/0x5e0
>       new_slab+0xc8/0x6bc
>       ___slab_alloc+0x3b8/0x640
>       kmem_cache_alloc+0x4b4/0x588
>       __debug_object_init+0x778/0x8b4
>       debug_object_init_on_stack+0x40/0x50
>       start_flush_work+0x16c/0x3f0
>       __flush_work+0xb8/0x124
>       flush_work+0x20/0x30
>       xlog_cil_force_lsn+0x88/0x204 [xfs]
>       xfs_log_force_lsn+0x128/0x1b8 [xfs]
>       xfs_file_fsync+0x3c4/0x488 [xfs]
>       vfs_fsync_range+0xb0/0xd0
>       generic_write_sync+0x80/0xa0 [xfs]
>       xfs_file_buffered_aio_write+0x66c/0x6e4 [xfs]
>       xfs_file_write_iter+0x1a0/0x218 [xfs]
>       __vfs_write+0x1cc/0x214
>       vfs_write+0x12c/0x1a4
>       ksys_write+0xb0/0x120
>       __arm64_sys_write+0x54/0x88
>       el0_svc_handler+0x170/0x240
>       el0_sync_handler+0x150/0x250
>       el0_sync+0x164/0x180
> 
>       other info that might help us debug this:
> 
> Chain exists of:
>   &(&zone->lock)->rlock --> &(&port->lock)->rlock --> &pool->lock/1
> 
> Possible unsafe locking scenario:
> 
>       CPU0                    CPU1
>       ----                    ----
>  lock(&pool->lock/1);
>                               lock(&(&port->lock)->rlock);
>                               lock(&pool->lock/1);
>  lock(&(&zone->lock)->rlock);
> 
>                *** DEADLOCK ***
> 
> 4 locks held by doio/49441:
> #0: a0ff00886fc27408 (sb_writers#8){.+.+}, at: vfs_write+0x118/0x1a4
> #1: 8fff00080810dfe0 (&xfs_nondir_ilock_class){++++}, at:
> xfs_ilock+0x2a8/0x300 [xfs]
> #2: ffff9000129f2390 (rcu_read_lock){....}, at:
> rcu_lock_acquire+0x8/0x38
> #3: 60ff000822352818 (&pool->lock/1){-.-.}, at:
> start_flush_work+0xd8/0x3f0
> 
>               stack backtrace:
> CPU: 48 PID: 49441 Comm: doio Tainted: G        W
> Hardware name: HPE Apollo 70             /C01_APACHE_MB         , BIOS
> L50_5.13_1.11 06/18/2019
> Call trace:
> dump_backtrace+0x0/0x248
> show_stack+0x20/0x2c
> dump_stack+0xe8/0x150
> print_circular_bug+0x368/0x380
> check_noncircular+0x28c/0x294
> validate_chain+0xf6c/0x2e2c
> __lock_acquire+0x868/0xc2c
> lock_acquire+0x320/0x360
> _raw_spin_lock+0x64/0x80
> rmqueue+0x138/0x2050
> get_page_from_freelist+0x474/0x688
> __alloc_pages_nodemask+0x3b4/0x18dc
> alloc_pages_current+0xd0/0xe0
> alloc_slab_page+0x2b4/0x5e0
> new_slab+0xc8/0x6bc
> ___slab_alloc+0x3b8/0x640
> kmem_cache_alloc+0x4b4/0x588
> __debug_object_init+0x778/0x8b4
> debug_object_init_on_stack+0x40/0x50
> start_flush_work+0x16c/0x3f0
> __flush_work+0xb8/0x124
> flush_work+0x20/0x30
> xlog_cil_force_lsn+0x88/0x204 [xfs]
> xfs_log_force_lsn+0x128/0x1b8 [xfs]
> xfs_file_fsync+0x3c4/0x488 [xfs]
> vfs_fsync_range+0xb0/0xd0
> generic_write_sync+0x80/0xa0 [xfs]
> xfs_file_buffered_aio_write+0x66c/0x6e4 [xfs]
> xfs_file_write_iter+0x1a0/0x218 [xfs]
> __vfs_write+0x1cc/0x214
> vfs_write+0x12c/0x1a4
> ksys_write+0xb0/0x120
> __arm64_sys_write+0x54/0x88
> el0_svc_handler+0x170/0x240
> el0_sync_handler+0x150/0x250
> el0_sync+0x164/0x180
> 
> [cai@lca.pw: add a commit log.]
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
> 
> Sergey, please let us know if you are fine with the Signed-off-by.
> 
> drivers/char/random.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 46afd14facb7..b90086c9836f 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -1688,8 +1688,9 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
> 	print_once = true;
> #endif
> 	if (__ratelimit(&unseeded_warning))
> -		pr_notice("random: %s called from %pS with crng_init=%d\n",
> -			  func_name, caller, crng_init);
> +		printk_deferred(KERN_NOTICE "random: %s called from %pS "
> +				"with crng_init=%d\n", func_name, caller,
> +				crng_init);
> }
> 
> /*
> -- 
> 1.8.3.1
> 


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] char/random: silence a lockdep splat with printk()
  2019-12-03 18:46 ` Qian Cai
@ 2019-12-05  1:00   ` Sergey Senozhatsky
  0 siblings, 0 replies; 3+ messages in thread
From: Sergey Senozhatsky @ 2019-12-05  1:00 UTC (permalink / raw)
  To: Qian Cai
  Cc: pmladek, tytso, sergey.senozhatsky.work, Arnd Bergmann, peterz,
	gregkh, linux-kernel, rostedt, linux-mm, Catalin Marinas,
	longman, dan.j.williams, will, tglx, linux-arm-kernel

Hi,

On (19/12/03 13:46), Qian Cai wrote:
> > On Nov 13, 2019, at 4:16 PM, Qian Cai <cai@lca.pw> wrote:
> > 
> > From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> > 
> > Sergey didn't like the locking order,
> > 
> > uart_port->lock  ->  tty_port->lock
> > 
> > uart_write (uart_port->lock)
> >  __uart_start
> >    pl011_start_tx
> >      pl011_tx_chars
> >        uart_write_wakeup
> >          tty_port_tty_wakeup
> >            tty_port_default
> >              tty_port_tty_get (tty_port->lock)
> > 
> > but those code is so old, and I have no clue how to de-couple it after
> > checking other locks in the splat. There is an onging effort to make all
> > printk() as deferred, so until that happens, workaround it for now as a
> > short-term fix.
> 
> Sergey, could we have a ACK from you so Ted might be able to merge?

Not sure if I can ACK it, but overall it makes sense to use deferred
printk there.

[..]
> 
> > [cai@lca.pw: add a commit log.]
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> > Signed-off-by: Qian Cai <cai@lca.pw>
> > ---
> > 
> > Sergey, please let us know if you are fine with the Signed-off-by.

A 'Reviewed-by' will suffice.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, back to index

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-13 21:16 [PATCH] char/random: silence a lockdep splat with printk() Qian Cai
2019-12-03 18:46 ` Qian Cai
2019-12-05  1:00   ` Sergey Senozhatsky

Linux-ARM-Kernel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/0 linux-arm-kernel/git/0.git
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/1 linux-arm-kernel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-arm-kernel linux-arm-kernel/ https://lore.kernel.org/linux-arm-kernel \
		linux-arm-kernel@lists.infradead.org
	public-inbox-index linux-arm-kernel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-arm-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git