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* Steven Rostedt <rostedt@goodmis.org> wrote: > Ingo, the following bug popped up. > > BUG: scheduling while atomic: modprobe/0x00000001/3083 > caller is schedule+0x84/0x111 > [<c0103fe2>] dump_stack+0x1e/0x20 (20) > [<c0323402>] __schedule+0x742/0xa94 (84) > [<c03237d8>] schedule+0x84/0x111 (28) > [<c0324a7b>] __down_mutex+0x56b/0x83a (116) > [<c0326bcf>] _spin_lock+0x1f/0x44 (28) > [<c0155070>] __kmalloc+0x6c/0x11d (36) > [<c021e989>] soft_cursor+0x61/0x1a8 (76) > [<c02175c4>] bit_cursor+0x2d3/0x588 (164) > [<c0212b4e>] fbcon_cursor+0x1be/0x307 (76) > [<c0213529>] fbcon_scroll+0x84/0xf5d (80) > [<c026bafd>] scrup+0xce/0xd8 (40) > [<c026d1a5>] lf+0x50/0x5d (28) > [<c026f3ad>] vt_console_print+0x116/0x2bb (56) > [<c011e9c4>] __call_console_drivers+0x47/0x56 (32) > [<c011ea4a>] _call_console_drivers+0x77/0x7e (24) > [<c011eaf6>] call_console_drivers+0xa5/0x183 (44) > [<c011f0af>] release_console_sem+0x2e/0xeb (32) > [<c011ef85>] vprintk+0x2aa/0x312 (108) > [<c011ecd9>] printk+0x1b/0x1d (20) > [<f8c2f04a>] usb_register_bus+0xf1/0x137 [usbcore] (36) > I didn't know that down_mutex could cause the scheduling while atomic. > It seems that the driver inside the vt_console failed to grab a lock, > and this will output, since printk does a raw_spin_lock_irqsave that > seems to also do a preempt_disable. (the kmallocs are GFP_ATOMIC). it's vprintk keeping preemption disabled, and then calling the console drivers, which may reschedule. The patch below should solve this. Ingo Index: linux/kernel/printk.c =================================================================== --- linux.orig/kernel/printk.c +++ linux/kernel/printk.c @@ -545,6 +545,7 @@ asmlinkage int vprintk(const char *fmt, /* This stops the holder of console_sem just where we want him */ spin_lock_irqsave(&logbuf_lock, flags); printk_cpu = smp_processor_id(); + preempt_enable(); /* Emit the output into the temporary buffer */ printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args); @@ -637,7 +638,6 @@ asmlinkage int vprintk(const char *fmt, spin_unlock_irqrestore(&logbuf_lock, flags); } out: - preempt_enable(); return printed_len; } EXPORT_SYMBOL(printk); - 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/ | |||||||||
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