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authorHendrik Brueckner <brueckner@linux.vnet.ibm.com>2009-01-14 23:15:44 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-01-16 16:15:16 +1100
commit7f8030d166f84b7413a0393819cb8b800484d5a9 (patch)
treee9cc1595c6c2a09e6bb4c656dfd69fe2b5c7d58d /drivers
parentb60c31d85a2a2f1a9c8623f1fb56e2688aa1e2b1 (diff)
downloadop-kernel-dev-7f8030d166f84b7413a0393819cb8b800484d5a9.zip
op-kernel-dev-7f8030d166f84b7413a0393819cb8b800484d5a9.tar.gz
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.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index 09676b4e..94e7e3c 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;
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