The patch titled
delay accounting taskstats interface: send tgid once locking fix
has been removed from the -mm tree. Its filename is
delay-accounting-taskstats-interface-send-tgid-once-locking.patch
This patch was dropped because it was folded into delay-accounting-taskstats-interface-send-tgid-once.patch
------------------------------------------------------
Subject: delay accounting taskstats interface: send tgid once locking fix
From: Shailabh Nagar <nagar@xxxxxxxxxxxxxx>
Use irqsave variants of spin_lock for newly introduced
tsk->signal->stats_lock The lock is nested within tasklist_lock as part of
release_task() and hence there is possibility of a AB-BA deadlock if a
timer interrupt occurs while stats_lock is held.
Thanks to Arjan van de Ven for pointing out the lock bug (akpm: found by the
locking validator).
The patch conservatively converts all use of stats_lock to irqsave variant
rather than only the call within taskstats_tgid_free which is the function
called within tasklist_lock protection.
Signed-off-by: Shailabh Nagar <nagar@xxxxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/taskstats_kern.h | 11 +++++++----
kernel/taskstats.c | 16 ++++++++++------
2 files changed, 17 insertions(+), 10 deletions(-)
diff -puN include/linux/taskstats_kern.h~delay-accounting-taskstats-interface-send-tgid-once-locking include/linux/taskstats_kern.h
--- a/include/linux/taskstats_kern.h~delay-accounting-taskstats-interface-send-tgid-once-locking
+++ a/include/linux/taskstats_kern.h
@@ -39,17 +39,18 @@ static inline void taskstats_tgid_init(s
static inline void taskstats_tgid_alloc(struct signal_struct *sig)
{
struct taskstats *stats;
+ unsigned long flags;
stats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
if (!stats)
return;
- spin_lock(&sig->stats_lock);
+ spin_lock_irqsave(&sig->stats_lock, flags);
if (!sig->stats) {
sig->stats = stats;
stats = NULL;
}
- spin_unlock(&sig->stats_lock);
+ spin_unlock_irqrestore(&sig->stats_lock, flags);
if (stats)
kmem_cache_free(taskstats_cache, stats);
@@ -58,12 +59,14 @@ static inline void taskstats_tgid_alloc(
static inline void taskstats_tgid_free(struct signal_struct *sig)
{
struct taskstats *stats = NULL;
- spin_lock(&sig->stats_lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&sig->stats_lock, flags);
if (sig->stats) {
stats = sig->stats;
sig->stats = NULL;
}
- spin_unlock(&sig->stats_lock);
+ spin_unlock_irqrestore(&sig->stats_lock, flags);
if (stats)
kmem_cache_free(taskstats_cache, stats);
}
diff -puN kernel/taskstats.c~delay-accounting-taskstats-interface-send-tgid-once-locking kernel/taskstats.c
--- a/kernel/taskstats.c~delay-accounting-taskstats-interface-send-tgid-once-locking
+++ a/kernel/taskstats.c
@@ -133,6 +133,7 @@ static int fill_tgid(pid_t tgid, struct
struct taskstats *stats)
{
struct task_struct *tsk, *first;
+ unsigned long flags;
/*
* Add additional stats from live tasks except zombie thread group
@@ -152,10 +153,10 @@ static int fill_tgid(pid_t tgid, struct
get_task_struct(first);
/* Start with stats from dead tasks */
- spin_lock(&first->signal->stats_lock);
+ spin_lock_irqsave(&first->signal->stats_lock, flags);
if (first->signal->stats)
memcpy(stats, first->signal->stats, sizeof(*stats));
- spin_unlock(&first->signal->stats_lock);
+ spin_unlock_irqrestore(&first->signal->stats_lock, flags);
tsk = first;
read_lock(&tasklist_lock);
@@ -185,7 +186,9 @@ static int fill_tgid(pid_t tgid, struct
static void fill_tgid_exit(struct task_struct *tsk)
{
- spin_lock(&tsk->signal->stats_lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&tsk->signal->stats_lock, flags);
if (!tsk->signal->stats)
goto ret;
@@ -197,7 +200,7 @@ static void fill_tgid_exit(struct task_s
*/
delayacct_add_tsk(tsk->signal->stats, tsk);
ret:
- spin_unlock(&tsk->signal->stats_lock);
+ spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);
return;
}
@@ -268,13 +271,14 @@ void taskstats_exit_send(struct task_str
size_t size;
int is_thread_group;
struct nlattr *na;
+ unsigned long flags;
if (!family_registered || !tidstats)
return;
- spin_lock(&tsk->signal->stats_lock);
+ spin_lock_irqsave(&tsk->signal->stats_lock, flags);
is_thread_group = tsk->signal->stats ? 1 : 0;
- spin_unlock(&tsk->signal->stats_lock);
+ spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);
rc = 0;
/*
_
Patches currently in -mm which might be from nagar@xxxxxxxxxxxxxx are
per-task-delay-accounting-setup.patch
per-task-delay-accounting-sync-block-i-o-and-swapin-delay-collection.patch
per-task-delay-accounting-cpu-delay-collection-via-schedstats.patch
per-task-delay-accounting-utilities-for-genetlink-usage.patch
per-task-delay-accounting-taskstats-interface.patch
per-task-delay-accounting-delay-accounting-usage-of-taskstats-interface.patch
per-task-delay-accounting-documentation.patch
per-task-delay-accounting-proc-export-of-aggregated-block-i-o-delays.patch
delay-accounting-taskstats-interface-send-tgid-once.patch
delay-accounting-taskstats-interface-send-tgid-once-locking.patch
per-task-delay-accounting-avoid-send-without-listeners.patch
task-watchers-register-per-task-delay-accounting.patch
-
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