From d5a877e8dd409d8c702986d06485c374b705d340 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Sun, 24 May 2009 13:03:43 -0700 Subject: async: make sure independent async domains can't accidentally entangle The problem occurs when async_synchronize_full_domain() is called when the async_pending list is not empty. This will cause lowest_running() to return the cookie of the first entry on the async_pending list, which might be nothing at all to do with the domain being asked for and thus cause the domain synchronization to wait for an unrelated domain. This can cause a deadlock if domain synchronization is used from one domain to wait for another. Fix by running over the async_pending list to see if any pending items actually belong to our domain (and return their cookies if they do). Signed-off-by: James Bottomley Signed-off-by: Arjan van de Ven Signed-off-by: Linus Torvalds --- kernel/async.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) (limited to 'kernel/async.c') diff --git a/kernel/async.c b/kernel/async.c index 968ef9457d4..50540301ed0 100644 --- a/kernel/async.c +++ b/kernel/async.c @@ -92,19 +92,23 @@ extern int initcall_debug; static async_cookie_t __lowest_in_progress(struct list_head *running) { struct async_entry *entry; + async_cookie_t ret = next_cookie; /* begin with "infinity" value */ + if (!list_empty(running)) { entry = list_first_entry(running, struct async_entry, list); - return entry->cookie; - } else if (!list_empty(&async_pending)) { - entry = list_first_entry(&async_pending, - struct async_entry, list); - return entry->cookie; - } else { - /* nothing in progress... next_cookie is "infinity" */ - return next_cookie; + ret = entry->cookie; } + if (!list_empty(&async_pending)) { + list_for_each_entry(entry, &async_pending, list) + if (entry->running == running) { + ret = entry->cookie; + break; + } + } + + return ret; } static async_cookie_t lowest_in_progress(struct list_head *running) -- cgit v1.2.3-70-g09d2 From 3af968e066d593bc4dacc021715f3e95ddf0996f Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 8 Jun 2009 12:31:53 -0700 Subject: async: Fix lack of boot-time console due to insufficient synchronization Our async work synchronization was broken by "async: make sure independent async domains can't accidentally entangle" (commit d5a877e8dd409d8c702986d06485c374b705d340), because it would report the wrong lowest active async ID when there was both running and pending async work. This caused things like no being able to read the root filesystem, resulting in missing console devices and inability to run 'init', causing a boot-time panic. This fixes it by properly returning the lowest pending async ID: if there is any running async work, that will have a lower ID than any pending work, and we should _not_ look at the pending work list. There were alternative patches from Jaswinder and James, but this one also cleans up the code by removing the pointless 'ret' variable and the unnecesary testing for an empty list around 'for_each_entry()' (if the list is empty, the for_each_entry() thing just won't execute). Fixes-bug: http://bugzilla.kernel.org/show_bug.cgi?id=13474 Reported-and-tested-by: Chris Clayton Cc: Jaswinder Singh Rajput Cc: James Bottomley Cc: Arjan van de Ven Signed-off-by: Linus Torvalds --- kernel/async.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) (limited to 'kernel/async.c') diff --git a/kernel/async.c b/kernel/async.c index 50540301ed0..27235f5de19 100644 --- a/kernel/async.c +++ b/kernel/async.c @@ -92,23 +92,18 @@ extern int initcall_debug; static async_cookie_t __lowest_in_progress(struct list_head *running) { struct async_entry *entry; - async_cookie_t ret = next_cookie; /* begin with "infinity" value */ if (!list_empty(running)) { entry = list_first_entry(running, struct async_entry, list); - ret = entry->cookie; + return entry->cookie; } - if (!list_empty(&async_pending)) { - list_for_each_entry(entry, &async_pending, list) - if (entry->running == running) { - ret = entry->cookie; - break; - } - } + list_for_each_entry(entry, &async_pending, list) + if (entry->running == running) + return entry->cookie; - return ret; + return next_cookie; /* "infinity" value */ } static async_cookie_t lowest_in_progress(struct list_head *running) -- cgit v1.2.3-70-g09d2