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List: linux-mm-commits
Subject: + task_work_add-generic-process-context-callbacks.patch added to -mm tree
From: akpm () linux-foundation ! org
Date: 2012-04-30 23:50:50
Message-ID: 20120430235051.5AB12A04C2 () akpm ! mtv ! corp ! google ! com
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The patch titled
Subject: task_work_add: generic process-context callbacks
has been added to the -mm tree. Its filename is
task_work_add-generic-process-context-callbacks.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Oleg Nesterov <oleg@redhat.com>
Subject: task_work_add: generic process-context callbacks
Provide a simple mechanism that allows running code in the (nonatomic)
context of the arbitrary task.
The caller does task_work_add(task, task_work) and this task executes
task_work->func() either from do_notify_resume() or from do_exit(). The
callback can rely on PF_EXITING to detect the latter case.
"struct task_work" can be embedded in another struct, still it has "void
*data" to handle the most common/simple case.
This allows us to kill the ->replacement_session_keyring hack, and
potentially this can have more users.
Performance-wise, this adds 2 "unlikely(!hlist_empty())" checks into
tracehook_notify_resume() and do_exit(). But at the same time we can
remove the "replacement_session_keyring != NULL" checks from
arch/*/signal.c and exit_creds().
Note: task_work_add/task_work_run abuses ->pi_lock. This is only because
this lock is already used by lookup_pi_state() to synchronize with
do_exit() setting PF_EXITING. Fortunately the scope of this lock in
task_work.c is really tiny, and the code is unlikely anyway.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Gordeev <agordeev@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Smith <dsmith@redhat.com>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
include/linux/sched.h | 2
include/linux/task_work.h | 33 ++++++++++++++
include/linux/tracehook.h | 13 ++++-
kernel/Makefile | 2
kernel/exit.c | 5 +-
kernel/fork.c | 1
kernel/task_work.c | 84 ++++++++++++++++++++++++++++++++++++
7 files changed, 136 insertions(+), 4 deletions(-)
diff -puN include/linux/sched.h~task_work_add-generic-process-context-callbacks \
include/linux/sched.h
--- a/include/linux/sched.h~task_work_add-generic-process-context-callbacks
+++ a/include/linux/sched.h
@@ -1455,6 +1455,8 @@ struct task_struct {
int (*notifier)(void *priv);
void *notifier_data;
sigset_t *notifier_mask;
+ struct hlist_head task_works;
+
struct audit_context *audit_context;
#ifdef CONFIG_AUDITSYSCALL
uid_t loginuid;
diff -puN /dev/null include/linux/task_work.h
--- /dev/null
+++ a/include/linux/task_work.h
@@ -0,0 +1,33 @@
+#ifndef _LINUX_TASK_WORK_H
+#define _LINUX_TASK_WORK_H
+
+#include <linux/list.h>
+#include <linux/sched.h>
+
+struct task_work;
+typedef void (*task_work_func_t)(struct task_work *);
+
+struct task_work {
+ struct hlist_node hlist;
+ task_work_func_t func;
+ void *data;
+};
+
+static inline void
+init_task_work(struct task_work *twork, task_work_func_t func, void *data)
+{
+ twork->func = func;
+ twork->data = data;
+}
+
+int task_work_add(struct task_struct *task, struct task_work *twork, bool);
+struct task_work *task_work_cancel(struct task_struct *, task_work_func_t);
+void task_work_run(void);
+
+static inline void exit_task_work(struct task_struct *task)
+{
+ if (unlikely(!hlist_empty(&task->task_works)))
+ task_work_run();
+}
+
+#endif /* _LINUX_TASK_WORK_H */
diff -puN include/linux/tracehook.h~task_work_add-generic-process-context-callbacks \
include/linux/tracehook.h
--- a/include/linux/tracehook.h~task_work_add-generic-process-context-callbacks
+++ a/include/linux/tracehook.h
@@ -49,6 +49,7 @@
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/security.h>
+#include <linux/task_work.h>
struct linux_binprm;
/*
@@ -153,7 +154,6 @@ static inline void tracehook_signal_hand
ptrace_notify(SIGTRAP);
}
-#ifdef TIF_NOTIFY_RESUME
/**
* set_notify_resume - cause tracehook_notify_resume() to be called
* @task: task that will call tracehook_notify_resume()
@@ -165,8 +165,10 @@ static inline void tracehook_signal_hand
*/
static inline void set_notify_resume(struct task_struct *task)
{
+#ifdef TIF_NOTIFY_RESUME
if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
kick_process(task);
+#endif
}
/**
@@ -184,7 +186,14 @@ static inline void set_notify_resume(str
*/
static inline void tracehook_notify_resume(struct pt_regs *regs)
{
+ /*
+ * The caller just cleared TIF_NOTIFY_RESUME. This barrier
+ * pairs with task_work_add()->set_notify_resume() after
+ * hlist_add_head(task->task_works);
+ */
+ smp_mb__after_clear_bit();
+ if (unlikely(!hlist_empty(¤t->task_works)))
+ task_work_run();
}
-#endif /* TIF_NOTIFY_RESUME */
#endif /* <linux/tracehook.h> */
diff -puN kernel/Makefile~task_work_add-generic-process-context-callbacks \
kernel/Makefile
--- a/kernel/Makefile~task_work_add-generic-process-context-callbacks
+++ a/kernel/Makefile
@@ -5,7 +5,7 @@
obj-y = fork.o exec_domain.o panic.o printk.o \
cpu.o exit.o itimer.o time.o softirq.o resource.o \
sysctl.o sysctl_binary.o capability.o ptrace.o timer.o user.o \
- signal.o sys.o kmod.o workqueue.o pid.o \
+ signal.o sys.o kmod.o workqueue.o pid.o task_work.o \
rcupdate.o extable.o params.o posix-timers.o \
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
diff -puN kernel/exit.c~task_work_add-generic-process-context-callbacks kernel/exit.c
--- a/kernel/exit.c~task_work_add-generic-process-context-callbacks
+++ a/kernel/exit.c
@@ -946,11 +946,14 @@ void do_exit(long code)
exit_signals(tsk); /* sets PF_EXITING */
/*
* tsk->flags are checked in the futex code to protect against
- * an exiting task cleaning up the robust pi futexes.
+ * an exiting task cleaning up the robust pi futexes, and in
+ * task_work_add() to avoid the race with exit_task_work().
*/
smp_mb();
raw_spin_unlock_wait(&tsk->pi_lock);
+ exit_task_work(tsk);
+
exit_irq_thread();
if (unlikely(in_atomic()))
diff -puN kernel/fork.c~task_work_add-generic-process-context-callbacks kernel/fork.c
--- a/kernel/fork.c~task_work_add-generic-process-context-callbacks
+++ a/kernel/fork.c
@@ -1391,6 +1391,7 @@ static struct task_struct *copy_process(
*/
p->group_leader = p;
INIT_LIST_HEAD(&p->thread_group);
+ INIT_HLIST_HEAD(&p->task_works);
/* Now that the task is set up, run cgroup callbacks if
* necessary. We need to run them before the task is visible
diff -puN /dev/null kernel/task_work.c
--- /dev/null
+++ a/kernel/task_work.c
@@ -0,0 +1,84 @@
+#include <linux/spinlock.h>
+#include <linux/task_work.h>
+#include <linux/tracehook.h>
+
+int
+task_work_add(struct task_struct *task, struct task_work *twork, bool notify)
+{
+ unsigned long flags;
+ int err = -ESRCH;
+
+#ifndef TIF_NOTIFY_RESUME
+ if (notify)
+ return -ENOTSUPP;
+#endif
+ /*
+ * We must not insert the new work if the task has already passed
+ * exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait()
+ * and check PF_EXITING under pi_lock.
+ */
+ raw_spin_lock_irqsave(&task->pi_lock, flags);
+ if (likely(!(task->flags & PF_EXITING))) {
+ hlist_add_head(&twork->hlist, &task->task_works);
+ err = 0;
+ }
+ raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+
+ /* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
+ if (likely(!err) && notify)
+ set_notify_resume(task);
+ return err;
+}
+
+struct task_work *
+task_work_cancel(struct task_struct *task, task_work_func_t func)
+{
+ unsigned long flags;
+ struct task_work *twork;
+ struct hlist_node *pos;
+
+ raw_spin_lock_irqsave(&task->pi_lock, flags);
+ hlist_for_each_entry(twork, pos, &task->task_works, hlist) {
+ if (twork->func == func) {
+ hlist_del(&twork->hlist);
+ goto found;
+ }
+ }
+ twork = NULL;
+ found:
+ raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+
+ return twork;
+}
+
+void task_work_run(void)
+{
+ struct task_struct *task = current;
+ struct hlist_head task_works;
+ struct hlist_node *pos;
+
+ raw_spin_lock_irq(&task->pi_lock);
+ hlist_move_list(&task->task_works, &task_works);
+ raw_spin_unlock_irq(&task->pi_lock);
+
+ if (unlikely(hlist_empty(&task_works)))
+ return;
+ /*
+ * We use hlist to save the space in task_struct, but we want fifo.
+ * Find the last entry, the list should be short, then process them
+ * in reverse order.
+ */
+ for (pos = task_works.first; pos->next; pos = pos->next)
+ ;
+
+ for (;;) {
+ struct hlist_node **pprev = pos->pprev;
+ struct task_work *twork = container_of(pos, struct task_work,
+ hlist);
+ twork->func(twork);
+
+ if (pprev == &task_works.first)
+ break;
+ pos = container_of(pprev, struct hlist_node, next);
+ }
+}
_
Subject: Subject: task_work_add: generic process-context callbacks
Patches currently in -mm which might be from oleg@redhat.com are
linux-next.patch
avr32-dont-mask-signals-in-the-error-path.patch
avr32-use-set_current_blocked-in-handle_signal-sys_rt_sigreturn.patch
avr32-use-block_sigmask.patch
m32r-use-set_current_blocked-and-block_sigmask.patch
m68k-use-set_current_blocked-and-block_sigmask.patch
mn10300-use-set_current_blocked-and-block_sigmask.patch
cris-use-set_current_blocked-and-block_sigmask.patch
ia64-use-set_current_blocked-and-block_sigmask.patch
microblaze-dont-reimplement-force_sigsegv.patch
microblaze-no-need-to-reset-handler-if-sa_oneshot.patch
microblaze-fix-signal-masking.patch
microblaze-use-set_current_blocked-and-block_sigmask.patch
score-dont-mask-signals-if-we-fail-to-setup-signal-stack.patch
score-use-set_current_blocked-and-block_sigmask.patch
h8300-use-set_current_blocked-and-block_sigmask.patch
unicore32-use-block_sigmask.patch
blackfin-use-set_current_blocked-and-block_sigmask.patch
mm-fork-fix-overflow-in-vma-length-when-copying-mmap-on-clone.patch
mm-correctly-synchronize-rss-counters-at-exit-exec.patch
frv-use-set_current_blocked-and-block_sigmask.patch
parisc-use-set_current_blocked-and-block_sigmask.patch
task_work_add-generic-process-context-callbacks.patch
genirq-reimplement-exit_irq_thread-hook-via-task_work_add.patch
hexagon-do_notify_resume-needs-tracehook_notify_resume.patch
keys-change-keyctl_session_to_parent-to-use-task_work_add.patch
keys-kill-the-dummy-key_replace_session_keyring.patch
keys-kill-task_struct-replacement_session_keyring.patch
kmod-unexport-call_usermodehelper_freeinfo.patch
kmod-convert-two-call-sites-to-call_usermodehelper_fns.patch
kmod-move-call_usermodehelper_fns-to-c-file-and-unexport-all-its-helpers.patch
cred-remove-task_is_dead-from-__task_cred-validation.patch
stack-usage-add-pid-to-warning-printk-in-check_stack_usage.patch
proc-clean-up-proc-pid-environ-handling.patch
proc-unify-ptrace_may_access-locking-code.patch
proc-remove-mm_for_maps.patch
proc-use-mm_access-instead-of-ptrace_may_access.patch
proc-use-is_err_or_null.patch
fork-call-complete_vfork_done-after-clearing-child_tid-and-flushing-rss-counters.patch
cpu-introduce-clear_tasks_mm_cpumask-helper.patch
arm-use-clear_tasks_mm_cpumask.patch
powerpc-use-clear_tasks_mm_cpumask.patch
sh-use-clear_tasks_mm_cpumask.patch
blackfin-a-couple-of-task-mm-handling-fixes.patch
blackfin-fix-possible-deadlock-in-decode_address.patch
um-should-hold-tasklist_lock-while-traversing-processes.patch
um-fix-possible-race-on-task-mm.patch
um-properly-check-all-process-threads-for-a-live-mm.patch
aio-vfs-cleanup-of-rw_copy_check_uvector-and-compat_rw_copy_check_uvector.patch
sysctl-make-kernelns_last_pid-control-being-checkpoint_restore-dependent.patch
fs-proc-introduce-proc-pid-task-tid-children-entry-v9.patch
fs-proc-introduce-proc-pid-task-tid-children-entry-v9-fix.patch
c-r-prctl-add-ability-to-set-new-mm_struct-exe_file.patch
c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-update-after-mm-num_exe_file_vmas-removal.patch
c-r-prctl-add-ability-to-get-clear_tid_address.patch
c-r-prctl-drop-vma-flags-test-on-pr_set_mm_-stack-data-assignment.patch
--
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