• Antonino A. Daplas's avatar
    [PATCH] vt: printk: Fix framebuffer console triggering might_sleep assertion · 78944e54
    Antonino A. Daplas authored
    Reported by: Dave Jones
    
    Whilst printk'ing to both console and serial console, I got this...
    (2.6.18rc1)
    
    BUG: sleeping function called from invalid context at kernel/sched.c:4438
    in_atomic():0, irqs_disabled():1
    
    Call Trace:
     [<ffffffff80271db8>] show_trace+0xaa/0x23d
     [<ffffffff80271f60>] dump_stack+0x15/0x17
     [<ffffffff8020b9f8>] __might_sleep+0xb2/0xb4
     [<ffffffff8029232e>] __cond_resched+0x15/0x55
     [<ffffffff80267eb8>] cond_resched+0x3b/0x42
     [<ffffffff80268c64>] console_conditional_schedule+0x12/0x14
     [<ffffffff80368159>] fbcon_redraw+0xf6/0x160
     [<ffffffff80369c58>] fbcon_scroll+0x5d9/0xb52
     [<ffffffff803a43c4>] scrup+0x6b/0xd6
     [<ffffffff803a4453>] lf+0x24/0x44
     [<ffffffff803a7ff8>] vt_console_print+0x166/0x23d
     [<ffffffff80295528>] __call_console_drivers+0x65/0x76
     [<ffffffff80295597>] _call_console_drivers+0x5e/0x62
     [<ffffffff80217e3f>] release_console_sem+0x14b/0x232
     [<ffffffff8036acd6>] fb_flashcursor+0x279/0x2a6
     [<ffffffff80251e3f>] run_workqueue+0xa8/0xfb
     [<ffffffff8024e5e0>] worker_thread+0xef/0x122
     [<ffffffff8023660f>] kthread+0x100/0x136
     [<ffffffff8026419e>] child_rip+0x8/0x12
    
    This can occur when release_console_sem() is called but the log
    buffer still has contents that need to be flushed. The console drivers
    are called while the console_may_schedule flag is still true. The
    might_sleep() is triggered when fbcon calls console_conditional_schedule().
    
    Fix by setting console_may_schedule to zero earlier, before the call to the
    console drivers.
    Signed-off-by: default avatarAntonino Daplas <adaplas@pol.net>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    78944e54
printk.c 27.3 KB