Re: [PATCH] fbcon: Avoid deleting a timer in IRQ context
From: Andrey Wagin <hidden>
Date: 2015-05-27 11:19:07
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2015-05-21 10:58 GMT+03:00 Thierry Reding [off-list ref]:
From: Thierry Reding <redacted>
Commit 27a4c827c34a ("fbcon: use the cursor blink interval provided by
vt") unconditionally removes the cursor blink timer. Unfortunately that
wreaks havoc under some circumstances. An easily reproducible way is to
use both the framebuffer console and a debug serial port as the console
output for kernel messages (e.g. "console=ttyS0 console=tty1" on the
kernel command-line. Upon boot this triggers a warning from within the
del_timer_sync() function because it is called from IRQ context:
[ 5.070096] ------------[ cut here ]------------
[ 5.070110] WARNING: CPU: 0 PID: 0 at ../kernel/time/timer.c:1098 del_timer_sync+0x4c/0x54()
[ 5.070115] Modules linked in:
[ 5.070120] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.1.0-rc4-next-20150519 #1
[ 5.070123] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[ 5.070142] [] (unwind_backtrace) from [] (show_stack+0x10/0x14)
[ 5.070156] [] (show_stack) from [] (dump_stack+0x70/0xbc)
[ 5.070164] [] (dump_stack) from [] (warn_slowpath_common+0x74/0xb0)
[ 5.070169] [] (warn_slowpath_common) from [] (warn_slowpath_null+0x1c/0x24)
[ 5.070174] [] (warn_slowpath_null) from [] (del_timer_sync+0x4c/0x54)
[ 5.070183] [] (del_timer_sync) from [] (fbcon_del_cursor_timer+0x2c/0x40)
[ 5.070190] [] (fbcon_del_cursor_timer) from [] (fbcon_cursor+0x9c/0x180)
[ 5.070198] [] (fbcon_cursor) from [] (hide_cursor+0x30/0x98)
[ 5.070204] [] (hide_cursor) from [] (vt_console_print+0x2a8/0x340)
[ 5.070212] [] (vt_console_print) from [] (call_console_drivers.constprop.23+0xc8/0xec)
[ 5.070218] [] (call_console_drivers.constprop.23) from [] (console_unlock+0x498/0x4f0)
[ 5.070223] [] (console_unlock) from [] (vprintk_emit+0x1f0/0x508)
[ 5.070228] [] (vprintk_emit) from [] (vprintk_default+0x24/0x2c)
[ 5.070234] [] (vprintk_default) from [] (printk+0x70/0x88)
After which the system starts spewing all kinds of weird and seemingly
unrelated error messages.
This commit fixes this by restoring the condition under which the call
to fbcon_del_cursor_timer() happens.Tested-by: Andrew Vagin <redacted> It would be good to push this patch into linux-next asap. Without this patch I can't execute tests on linux-next. Thanks.
quoted hunk ↗ jump to hunk
Reported-by: Daniel Stone <redacted> Reported-by: Kevin Hilman <khilman@kernel.org> Tested-by: Kevin Hilman <redacted> Tested-by: Scot Doyle <redacted> Signed-off-by: Thierry Reding <redacted> --- drivers/video/console/fbcon.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c index 05b1d1a71ef9..658c34bb9076 100644 --- a/drivers/video/console/fbcon.c +++ b/drivers/video/console/fbcon.c@@ -1310,8 +1310,9 @@ static void fbcon_cursor(struct vc_data *vc, int mode) return; ops->cur_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms); - fbcon_del_cursor_timer(info); - if (!(vc->vc_cursor_type & 0x10)) + if (vc->vc_cursor_type & 0x10) + fbcon_del_cursor_timer(info); + else fbcon_add_cursor_timer(info); ops->cursor_flash = (mode = CM_ERASE) ? 0 : 1; --2.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/