Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=cc1ed7542c8c26af0f501da8006b9fce03e9aaca
Commit:     cc1ed7542c8c26af0f501da8006b9fce03e9aaca
Parent:     4a19542e5f694cd408a32c3d9dc593ba9366e2d7
Author:     Pierre Ossman <[EMAIL PROTECTED]>
AuthorDate: Sun Jul 15 23:40:35 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Mon Jul 16 09:05:45 2007 -0700

    init: wait for asynchronously scanned block devices
    
    Some buses (e.g.  USB and MMC) do their scanning of devices in the
    background, causing a race between them and prepare_namespace().  In order
    to be able to use these buses without an initrd, we now wait for the device
    specified in root= to actually show up.
    
    If the device never shows up than we will hang in an infinite loop.  In
    order to not mess with setups that reboot on panic, the feature must be
    turned on via the command line option "rootwait".
    
    [EMAIL PROTECTED]: root_wait can become static]
    Signed-off-by: Pierre Ossman <[EMAIL PROTECTED]>
    Cc: Al Viro <[EMAIL PROTECTED]>
    Cc: Christoph Hellwig <[EMAIL PROTECTED]>
    Signed-off-by: Adrian Bunk <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 Documentation/kernel-parameters.txt |    4 ++++
 init/do_mounts.c                    |   24 ++++++++++++++++++++++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/Documentation/kernel-parameters.txt 
b/Documentation/kernel-parameters.txt
index a0362d5..a571495 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1504,6 +1504,10 @@ and is between 256 and 4096 characters. It is defined in 
the file
 
        rootfstype=     [KNL] Set root filesystem type
 
+       rootwait        [KNL] Wait (indefinitely) for root device to show up.
+                       Useful for devices that are detected asynchronously
+                       (e.g. USB and MMC devices).
+
        rw              [KNL] Mount root device read-write on boot
 
        S               [KNL] Run init in single mode
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 46fe407..4efa1e5 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -25,6 +25,7 @@ int __initdata rd_doload;     /* 1 = load RAM disk, 0 = don't 
load */
 int root_mountflags = MS_RDONLY | MS_SILENT;
 char * __initdata root_device_name;
 static char __initdata saved_root_name[64];
+static int __initdata root_wait;
 
 dev_t ROOT_DEV;
 
@@ -216,6 +217,16 @@ static int __init root_dev_setup(char *line)
 
 __setup("root=", root_dev_setup);
 
+static int __init rootwait_setup(char *str)
+{
+       if (*str)
+               return 0;
+       root_wait = 1;
+       return 1;
+}
+
+__setup("rootwait", rootwait_setup);
+
 static char * __initdata root_mount_data;
 static int __init root_data_setup(char *str)
 {
@@ -438,11 +449,20 @@ void __init prepare_namespace(void)
                        root_device_name += 5;
        }
 
-       is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;
-
        if (initrd_load())
                goto out;
 
+       /* wait for any asynchronous scanning to complete */
+       if ((ROOT_DEV == 0) && root_wait) {
+               printk(KERN_INFO "Waiting for root device %s...\n",
+                       saved_root_name);
+               while (driver_probe_done() != 0 ||
+                       (ROOT_DEV = name_to_dev_t(saved_root_name)) == 0)
+                       msleep(100);
+       }
+
+       is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;
+
        if (is_floppy && rd_doload && rd_load_disk(0))
                ROOT_DEV = Root_RAM0;
 
-
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