[PATCH] kdump: introduce "reset_devices" command line option

Resetting the devices during driver initialization can be a costly
operation in terms of time (especially scsi devices).  This option can be
used by drivers to know that user forcibly wants the devices to be reset
during initialization.

This option can be useful while kernel is booting in unreliable
environment.  For ex.  during kdump boot where devices are in unknown
random state and BIOS execution has been skipped.

Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 255ec535bba803699f4608fc99b05810582b5c14..54983246930d1aeb922c3691ac0b5a96028d97ef 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1370,6 +1370,9 @@ running once the system is up.
                        Reserves a hole at the top of the kernel virtual
                        address space.
 
+       reset_devices   [KNL] Force drivers to reset the underlying device
+                       during initialization.
+
        resume=         [SWSUSP]
                        Specify the partition device for software suspend
 

diff --git a/include/linux/init.h b/include/linux/init.h
index 6667785dd1ff22d7452b716b380e7475158ee8b9..e92b1455d7afd8c908bfc0722be018a09c46c226 100644 (file)
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -68,6 +68,7 @@ extern initcall_t __security_initcall_start[], __security_initcall_end[];
 
 /* Defined in init/main.c */
 extern char saved_command_line[];
+extern unsigned int reset_devices;
 
 /* used by init/main.c */
 extern void setup_arch(char **);

diff --git a/init/main.c b/init/main.c
index 913e48d658ee1de1938edf62dfee2d497b02448f..0766e69712b2a86efa74caf3c5bd487bbbcd3753 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -127,6 +127,18 @@ static char *ramdisk_execute_command;
 /* Setup configured maximum number of CPUs to activate */
 static unsigned int max_cpus = NR_CPUS;
 
+/*
+ * If set, this is an indication to the drivers that reset the underlying
+ * device before going ahead with the initialization otherwise driver might
+ * rely on the BIOS and skip the reset operation.
+ *
+ * This is useful if kernel is booting in an unreliable environment.
+ * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
+ * skipped and devices will be in unknown state.
+ */
+unsigned int reset_devices;
+EXPORT_SYMBOL(reset_devices);
+
 /*
  * Setup routine for controlling SMP activation
  *
@@ -153,6 +165,14 @@ static int __init maxcpus(char *str)
 
 __setup("maxcpus=", maxcpus);
 
+static int __init set_reset_devices(char *str)
+{
+       reset_devices = 1;
+       return 1;
+}
+
+__setup("reset_devices", set_reset_devices);
+
 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
 static const char *panic_later, *panic_param;