Messages in this thread Patch in this message | | | From | ning.a.zhang@intel ... | Subject | [PATCH] init: no need to wait device probe | Date | Mon, 19 Mar 2018 10:55:08 +0800 |
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From: Zhang Ning <ning.a.zhang@intel.com>
there are 2 reasons for no need to wait device probe
reason 1: mount root device is very late in kernel initial stage. all initcalls are finished. that means most of probe functions are returned.
and deferred probe are also finished by late_initcall. only async probe driver are possible in probing.
no block devices, device-mapper or nfs are use async probe. so no need to wait device probe.
reason 2: let's check dd.c, probe_count is increased and decreased only in really_probe, and when really_probe returns, probe_count always be 0.
when someone really wants to wait device-B probe. but code looks like:
thread-1: thread-2: probe device-A; wait_for_device_probe(); msleep(30); probe device-B
when device-A probe finishes, thread-2 will be wakeup, but device-B is not probed.
wait_for_device_probe can't make sure the device you want is probed.
based on above 2 reasons, no need to wait for device probe.
Signed-off-by: Zhang Ning <ning.a.zhang@intel.com> --- init/do_mounts.c | 9 --------- init/do_mounts_md.c | 2 -- 2 files changed, 11 deletions(-)
diff --git a/init/do_mounts.c b/init/do_mounts.c index 7cf4f6dafd5f..a9fb2ad44964 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -555,15 +555,6 @@ void __init prepare_namespace(void) ssleep(root_delay); } - /* - * wait for the known devices to complete their probing - * - * Note: this is a potential source of long boot delays. - * For example, it is not atypical to wait 5 seconds here - * for the touchpad of a laptop to initialize. - */ - wait_for_device_probe(); - md_run_setup(); if (saved_root_name[0]) { diff --git a/init/do_mounts_md.c b/init/do_mounts_md.c index 3f733c760a8c..4aab3492e71d 100644 --- a/init/do_mounts_md.c +++ b/init/do_mounts_md.c @@ -292,8 +292,6 @@ static void __init autodetect_raid(void) printk(KERN_INFO "md: Waiting for all devices to be available before autodetect\n"); printk(KERN_INFO "md: If you don't use raid, use raid=noautodetect\n"); - wait_for_device_probe(); - fd = sys_open("/dev/md0", 0, 0); if (fd >= 0) { sys_ioctl(fd, RAID_AUTORUN, raid_autopart); -- 2.14.2
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