Messages in this thread Patch in this message | | | Date | Thu, 29 Nov 2001 13:10:59 +0000 | From | Russell King <> | Subject | Patch: Fix serial module use count (2.4.16 _and_ 2.5) |
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Hi,
The existing serial.c contains a nice module use count bug which is easily triggerable. Without anything connected to ttyS0, do:
stty -clocal -F /dev/ttyS0 stty -aF /dev/ttyS0
Hit ^c, lsmod shows use count of -1. Repeat to decrement further.
Here's a patch that fixes this bogosity - please see the comment within the patch for the reason.
Marcelo, please apply to both 2.4. Linus, please apply to 2.5 as a stop-gap until my new serial drivers are ready to be merged.
Thanks.
--- linux-orig/drivers/char/serial.c Tue Nov 13 12:37:12 2001 +++ linux/drivers/char/serial.c Thu Nov 29 13:07:52 2001 @@ -3133,6 +3133,10 @@ * enables interrupts for a serial port, linking in its async structure into * the IRQ chain. It also performs the serial-specific * initialization for the tty structure. + * + * Note that on failure, we don't decrement the module use count - the tty + * later will call rs_close, which will decrement it for us as long as + * tty->driver_data is set non-NULL. --rmk */ static int rs_open(struct tty_struct *tty, struct file * filp) { @@ -3153,10 +3157,8 @@ } tty->driver_data = info; info->tty = tty; - if (serial_paranoia_check(info, tty->device, "rs_open")) { - MOD_DEC_USE_COUNT; + if (serial_paranoia_check(info, tty->device, "rs_open")) return -ENODEV; - } #ifdef SERIAL_DEBUG_OPEN printk("rs_open %s%d, count = %d\n", tty->driver.name, info->line, @@ -3171,10 +3173,8 @@ */ if (!tmp_buf) { page = get_zeroed_page(GFP_KERNEL); - if (!page) { - MOD_DEC_USE_COUNT; + if (!page) return -ENOMEM; - } if (tmp_buf) free_page(page); else @@ -3188,7 +3188,6 @@ (info->flags & ASYNC_CLOSING)) { if (info->flags & ASYNC_CLOSING) interruptible_sleep_on(&info->close_wait); - MOD_DEC_USE_COUNT; #ifdef SERIAL_DO_RESTART return ((info->flags & ASYNC_HUP_NOTIFY) ? -EAGAIN : -ERESTARTSYS); @@ -3201,10 +3200,8 @@ * Start up serial port */ retval = startup(info); - if (retval) { - MOD_DEC_USE_COUNT; + if (retval) return retval; - } retval = block_til_ready(tty, filp, info); if (retval) { @@ -3212,7 +3209,6 @@ printk("rs_open returning after block_til_ready with %d\n", retval); #endif - MOD_DEC_USE_COUNT; return retval; }
-- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html
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