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| author | Hendrik Brueckner <brueckner@linux.vnet.ibm.com> | 2009-01-14 23:15:44 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-01-16 16:15:16 +1100 |
| commit | 7f8030d166f84b7413a0393819cb8b800484d5a9 (patch) | |
| tree | e9cc1595c6c2a09e6bb4c656dfd69fe2b5c7d58d /drivers | |
| parent | b60c31d85a2a2f1a9c8623f1fb56e2688aa1e2b1 (diff) | |
| download | linux-stable-7f8030d166f84b7413a0393819cb8b800484d5a9.tar.gz linux-stable-7f8030d166f84b7413a0393819cb8b800484d5a9.tar.bz2 linux-stable-7f8030d166f84b7413a0393819cb8b800484d5a9.zip | |
hvc_console: Remove tty->low_latency
This patch removes the tty->low_latency setting.
For irq based hvc_console backends the tty->low_latency must be set to 0,
because the tty_flip_buffer_push() function must not be called from IRQ context
(see drivers/char/tty_buffer.c).
For polled backends, the low_latency setting causes the bug trace below, because
tty_flip_buffer_push() is called within an atomic context and subsequent calls
might sleep due to mutex_lock.
BUG: sleeping function called from invalid context at /root/cvs/linux-2.6.git/kernel/mutex.c:207
in_atomic(): 1, irqs_disabled(): 0, pid: 748, name: khvcd
1 lock held by khvcd/748:
#0: (hvc_structs_lock){--..}, at: [<00000000002ceb50>] khvcd+0x58/0x12c
CPU: 0 Not tainted 2.6.29-rc1git #29
Process khvcd (pid: 748, task: 000000002fb9a480, ksp: 000000002f66bd78)
070000000000000a 000000002f66ba00 0000000000000002 (null)
000000002f66baa0 000000002f66ba18 000000002f66ba18 0000000000104f08
ffffffffffffc000 000000002f66bd78 (null) (null)
000000002f66ba00 000000000000000c 000000002f66ba00 000000002f66ba70
0000000000466af8 0000000000104f08 000000002f66ba00 000000002f66ba50
Call Trace:
([<0000000000104e7c>] show_trace+0x138/0x158)
[<0000000000104f62>] show_stack+0xc6/0xf8
[<0000000000105740>] dump_stack+0xb0/0xc0
[<000000000013144a>] __might_sleep+0x14e/0x17c
[<000000000045e226>] mutex_lock_nested+0x42/0x3b4
[<00000000002c443e>] echo_char_raw+0x3a/0x9c
[<00000000002c688c>] n_tty_receive_buf+0x1154/0x1208
[<00000000002ca0a2>] flush_to_ldisc+0x152/0x220
[<00000000002ca1da>] tty_flip_buffer_push+0x6a/0x90
[<00000000002cea74>] hvc_poll+0x244/0x2c8
[<00000000002ceb68>] khvcd+0x70/0x12c
[<000000000015bbd0>] kthread+0x68/0xa0
[<0000000000109d5a>] kernel_thread_starter+0x6/0xc
[<0000000000109d54>] kernel_thread_starter+0x0/0xc
1 lock held by khvcd/748:
#0: (hvc_structs_lock){--..}, at: [<00000000002ceb50>] khvcd+0x58/0x12c
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/char/hvc_console.c | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c index 09676b4e5d89..94e7e3c8c05a 100644 --- a/drivers/char/hvc_console.c +++ b/drivers/char/hvc_console.c @@ -318,8 +318,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp) } /* else count == 0 */ tty->driver_data = hp; - if (!hp->irq_requested) - tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */ hp->tty = tty; |