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Subject[RFC][PATCH 2/2] kernel: extract thread types from task_struct::flags
Free up a few more PF_flags by moving thread types out to their own variable.

Initially I compressed the types into less bits inside task_struct::flags, but
Thomas suggested I move them to their own field.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
fs/exec.c | 4 +-
fs/xfs/linux-2.6/xfs_aops.c | 2 -
include/linux/init_task.h | 3 +
include/linux/kvm_host.h | 4 +-
include/linux/sched.h | 79 +++++++++++++++++++++++++++-----------------
include/linux/swap.h | 2 -
kernel/exit.c | 3 +
kernel/fork.c | 12 +++++-
kernel/ptrace.c | 2 -
kernel/rtmutex-tester.c | 2 -
kernel/rtmutex_common.h | 2 -
kernel/sched.c | 7 ++-
kernel/workqueue.c | 4 +-
lib/is_single_threaded.c | 2 -
mm/oom_kill.c | 4 +-
mm/vmscan.c | 3 +
16 files changed, 83 insertions(+), 52 deletions(-)
Index: linux-2.6/fs/exec.c
===================================================================
--- linux-2.6.orig/fs/exec.c
+++ linux-2.6/fs/exec.c
@@ -1401,7 +1401,7 @@ int do_execve(const char * filename,
if (retval < 0)
goto out;

- current->flags &= ~PF_KTHREAD;
+ task_set_type(current, tt_user);
retval = search_binary_handler(bprm,regs);
if (retval < 0)
goto out;
@@ -1651,7 +1651,7 @@ static inline int zap_threads(struct tas
for_each_process(g) {
if (g == tsk->group_leader)
continue;
- if (g->flags & PF_KTHREAD)
+ if (task_type(g) >= tt_kernel)
continue;
p = g;
do {
Index: linux-2.6/fs/xfs/linux-2.6/xfs_aops.c
===================================================================
--- linux-2.6.orig/fs/xfs/linux-2.6/xfs_aops.c
+++ linux-2.6/fs/xfs/linux-2.6/xfs_aops.c
@@ -1067,7 +1067,7 @@ xfs_vm_writepage(
* filesystems like XFS, btrfs and ext4 have to take care of this
* by themselves.
*/
- if ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC)
+ if (task_type(current) != tt_kswapd && (current->flags & PF_MEMALLOC))
goto redirty;

/*
Index: linux-2.6/include/linux/init_task.h
===================================================================
--- linux-2.6.orig/include/linux/init_task.h
+++ linux-2.6/include/linux/init_task.h
@@ -117,7 +117,8 @@ extern struct cred init_cred;
.state = 0, \
.stack = &init_thread_info, \
.usage = ATOMIC_INIT(2), \
- .flags = PF_KTHREAD, \
+ .flags = 0, \
+ .threadtype = tt_kernel, \
.lock_depth = -1, \
.prio = MAX_PRIO-20, \
.static_prio = MAX_PRIO-20, \
Index: linux-2.6/include/linux/kvm_host.h
===================================================================
--- linux-2.6.orig/include/linux/kvm_host.h
+++ linux-2.6/include/linux/kvm_host.h
@@ -509,13 +509,13 @@ static inline int kvm_deassign_device(st
static inline void kvm_guest_enter(void)
{
account_system_vtime(current);
- current->flags |= PF_VCPU;
+ task_set_type(current, tt_vcpu);
}

static inline void kvm_guest_exit(void)
{
account_system_vtime(current);
- current->flags &= ~PF_VCPU;
+ task_set_type(current, tt_user);
}

static inline gpa_t gfn_to_gpa(gfn_t gfn)
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1168,12 +1168,26 @@ enum perf_event_task_context {
perf_nr_task_contexts,
};

+/*
+ * Types >= tt_kernel imply the old PF_KTHREAD
+ */
+enum thread_type {
+ tt_user = 0, /* I'm a normal userspace thread */
+ tt_vcpu, /* I'm a VCPU */
+ tt_kernel, /* I'm a normal kernel thread */
+ tt_worker, /* I'm a workqueue worker thread */
+ tt_kswapd, /* I'm a kswap daemon thread */
+ tt_mutex_tester, /* I'm a mutex tester thread */
+ tt_nr_max,
+};
+
struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
void *stack;
atomic_t usage;
unsigned int flags; /* per process flags, defined below */
unsigned int ptrace;
+ enum thread_type threadtype;

int lock_depth; /* BKL lock depth */

@@ -1691,36 +1705,41 @@ extern void thread_group_times(struct ta
/*
* Per process flags
*/
-#define PF_STARTING 0x00000002 /* being created */
-#define PF_EXITING 0x00000004 /* getting shut down */
-#define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */
-#define PF_VCPU 0x00000010 /* I'm a virtual CPU */
-#define PF_WQ_WORKER 0x00000020 /* I'm a workqueue worker */
-#define PF_FORKNOEXEC 0x00000040 /* forked but didn't exec */
-#define PF_MCE_PROCESS 0x00000080 /* process policy on mce errors */
-#define PF_SUPERPRIV 0x00000100 /* used super-user privileges */
-#define PF_DUMPCORE 0x00000200 /* dumped core */
-#define PF_SIGNALED 0x00000400 /* killed by a signal */
-#define PF_MEMALLOC 0x00000800 /* Allocating memory */
-#define PF_USED_MATH 0x00002000 /* if unset the fpu must be initialized before use */
-#define PF_FREEZING 0x00004000 /* freeze in progress. do not account to load */
-#define PF_NOFREEZE 0x00008000 /* this thread should not be frozen */
-#define PF_FROZEN 0x00010000 /* frozen for system suspend */
-#define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
-#define PF_KSWAPD 0x00040000 /* I am kswapd */
-#define PF_OOM_ORIGIN 0x00080000 /* Allocating much memory to others */
-#define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */
-#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
-#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */
-#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
-#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
-#define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */
-#define PF_THREAD_BOUND 0x04000000 /* Thread bound to specific cpu */
-#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */
-#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
-#define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
-#define PF_FREEZER_SKIP 0x40000000 /* Freezer should not count it as freezeable */
-#define PF_FREEZER_NOSIG 0x80000000 /* Freezer won't send signals to it */
+#define PF_STARTING 0x00000001 /* being created */
+#define PF_EXITING 0x00000002 /* getting shut down */
+#define PF_EXITPIDONE 0x00000004 /* pi exit done on shut down */
+#define PF_FORKNOEXEC 0x00000008 /* forked but didn't exec */
+#define PF_MCE_PROCESS 0x00000010 /* process policy on mce errors */
+#define PF_SUPERPRIV 0x00000020 /* used super-user privileges */
+#define PF_DUMPCORE 0x00000040 /* dumped core */
+#define PF_SIGNALED 0x00000080 /* killed by a signal */
+#define PF_MEMALLOC 0x00000100 /* Allocating memory */
+#define PF_USED_MATH 0x00000200 /* if unset the fpu must be initialized before use */
+#define PF_FREEZING 0x00000400 /* freeze in progress. do not account to load */
+#define PF_NOFREEZE 0x00000800 /* this thread should not be frozen */
+#define PF_FROZEN 0x00001000 /* frozen for system suspend */
+#define PF_FREEZER_SKIP 0x00002000 /* Freezer should not count it as freezeable */
+#define PF_FREEZER_NOSIG 0x00004000 /* Freezer won't send signals to it */
+#define PF_FSTRANS 0x00008000 /* inside a filesystem transaction */
+#define PF_OOM_ORIGIN 0x00010000 /* Allocating much memory to others */
+#define PF_LESS_THROTTLE 0x00020000 /* Throttle me less: I clean memory */
+#define PF_RANDOMIZE 0x00040000 /* randomize virtual address space */
+#define PF_SWAPWRITE 0x00080000 /* Allowed to write to swap */
+#define PF_SPREAD_PAGE 0x00100000 /* Spread page cache over cpuset */
+#define PF_SPREAD_SLAB 0x00200000 /* Spread some slab caches over cpuset */
+#define PF_THREAD_BOUND 0x00400000 /* Thread bound to specific cpu */
+#define PF_MCE_EARLY 0x00800000 /* Early kill for mce process policy */
+#define PF_MEMPOLICY 0x01000000 /* Non-default NUMA mempolicy */
+
+static inline void task_set_type(struct task_struct *p, enum thread_type type)
+{
+ p->threadtype = type;
+}
+
+static inline enum thread_type task_type(struct task_struct *p)
+{
+ return p->threadtype;
+}

/*
* Only the _current_ task can read/write to tsk->flags, but other
Index: linux-2.6/include/linux/swap.h
===================================================================
--- linux-2.6.orig/include/linux/swap.h
+++ linux-2.6/include/linux/swap.h
@@ -23,7 +23,7 @@ struct bio;

static inline int current_is_kswapd(void)
{
- return current->flags & PF_KSWAPD;
+ return task_type(current) == tt_kswapd;
}

/*
Index: linux-2.6/kernel/exit.c
===================================================================
--- linux-2.6.orig/kernel/exit.c
+++ linux-2.6/kernel/exit.c
@@ -431,7 +431,8 @@ void daemonize(const char *name, ...)
* We don't want to have TIF_FREEZE set if the system-wide hibernation
* or suspend transition begins right now.
*/
- current->flags |= (PF_NOFREEZE | PF_KTHREAD);
+ task_set_type(current, tt_kernel);
+ current->flags |= PF_NOFREEZE;

if (current->nsproxy != &init_nsproxy) {
get_nsproxy(&init_nsproxy);
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c
+++ linux-2.6/kernel/fork.c
@@ -570,7 +570,7 @@ struct mm_struct *get_task_mm(struct tas
task_lock(task);
mm = task->mm;
if (mm) {
- if (task->flags & PF_KTHREAD)
+ if (task_type(task) >= tt_kernel)
mm = NULL;
else
atomic_inc(&mm->mm_users);
@@ -910,8 +910,16 @@ static int copy_signal(unsigned long clo
static void copy_flags(unsigned long clone_flags, struct task_struct *p)
{
unsigned long new_flags = p->flags;
+ unsigned long new_type;

- new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
+ if (task_type(p) >= tt_kernel)
+ new_type = tt_kernel;
+ else
+ new_type = tt_user;
+
+ task_set_type(p, new_type);
+
+ new_flags &= ~PF_SUPERPRIV;
new_flags |= PF_FORKNOEXEC;
new_flags |= PF_STARTING;
p->flags = new_flags;
Index: linux-2.6/kernel/ptrace.c
===================================================================
--- linux-2.6.orig/kernel/ptrace.c
+++ linux-2.6/kernel/ptrace.c
@@ -170,7 +170,7 @@ int ptrace_attach(struct task_struct *ta
audit_ptrace(task);

retval = -EPERM;
- if (unlikely(task->flags & PF_KTHREAD))
+ if (unlikely(task_type(task) >= tt_kernel))
goto out;
if (same_thread_group(task, current))
goto out;
Index: linux-2.6/kernel/rtmutex-tester.c
===================================================================
--- linux-2.6.orig/kernel/rtmutex-tester.c
+++ linux-2.6/kernel/rtmutex-tester.c
@@ -259,7 +259,7 @@ static int test_func(void *data)
struct test_thread_data *td = data;
int ret;

- current->flags |= PF_MUTEX_TESTER;
+ task_set_type(current, tt_mutex_tester);
set_freezable();
allow_signal(SIGHUP);

Index: linux-2.6/kernel/rtmutex_common.h
===================================================================
--- linux-2.6.orig/kernel/rtmutex_common.h
+++ linux-2.6/kernel/rtmutex_common.h
@@ -26,7 +26,7 @@ extern void schedule_rt_mutex_test(struc

#define schedule_rt_mutex(_lock) \
do { \
- if (!(current->flags & PF_MUTEX_TESTER)) \
+ if (task_type(current) != tt_mutex_tester) \
schedule(); \
else \
schedule_rt_mutex_test(_lock); \
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2322,7 +2322,7 @@ static inline void ttwu_post_activation(
}
#endif
/* if a worker is waking up, notify workqueue */
- if ((p->flags & PF_WQ_WORKER) && success)
+ if (task_type(p) == tt_worker && success)
wq_worker_waking_up(p, cpu_of(rq));
}

@@ -3380,7 +3380,8 @@ void account_system_time(struct task_str
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
cputime64_t tmp;

- if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
+
+ if (task_type(p) == tt_vcpu && (irq_count() - hardirq_offset == 0)) {
account_guest_time(p, cputime, cputime_scaled);
return;
}
@@ -3772,7 +3773,7 @@ asmlinkage void __sched schedule(void)
* task to maintain concurrency. If so, wake
* up the task.
*/
- if (prev->flags & PF_WQ_WORKER) {
+ if (task_type(prev) == tt_worker) {
struct task_struct *to_wakeup;

to_wakeup = wq_worker_sleeping(prev, cpu);
Index: linux-2.6/kernel/workqueue.c
===================================================================
--- linux-2.6.orig/kernel/workqueue.c
+++ linux-2.6/kernel/workqueue.c
@@ -1888,14 +1888,14 @@ static int worker_thread(void *__worker)
struct global_cwq *gcwq = worker->gcwq;

/* tell the scheduler that this is a workqueue worker */
- worker->task->flags |= PF_WQ_WORKER;
+ task_set_type(worker->task, tt_worker);
woke_up:
spin_lock_irq(&gcwq->lock);

/* DIE can be set only while we're idle, checking here is enough */
if (worker->flags & WORKER_DIE) {
spin_unlock_irq(&gcwq->lock);
- worker->task->flags &= ~PF_WQ_WORKER;
+ task_set_type(worker->task, tt_kernel);
return 0;
}

Index: linux-2.6/lib/is_single_threaded.c
===================================================================
--- linux-2.6.orig/lib/is_single_threaded.c
+++ linux-2.6/lib/is_single_threaded.c
@@ -31,7 +31,7 @@ bool current_is_single_threaded(void)
ret = false;
rcu_read_lock();
for_each_process(p) {
- if (unlikely(p->flags & PF_KTHREAD))
+ if (unlikely(task_type(p) >= tt_kernel))
continue;
if (unlikely(p == task->group_leader))
continue;
Index: linux-2.6/mm/oom_kill.c
===================================================================
--- linux-2.6.orig/mm/oom_kill.c
+++ linux-2.6/mm/oom_kill.c
@@ -126,7 +126,7 @@ static bool oom_unkillable_task(struct t
{
if (is_global_init(p))
return true;
- if (p->flags & PF_KTHREAD)
+ if (task_type(p) >= tt_kernel)
return true;

/* When mem_cgroup_out_of_memory() and p is not member of the group */
@@ -356,7 +356,7 @@ static void dump_tasks(const struct mem_

pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n");
for_each_process(p) {
- if (p->flags & PF_KTHREAD)
+ if (task_type(p) >= tt_kernel)
continue;
if (mem && !task_in_mem_cgroup(p, mem))
continue;
Index: linux-2.6/mm/vmscan.c
===================================================================
--- linux-2.6.orig/mm/vmscan.c
+++ linux-2.6/mm/vmscan.c
@@ -2316,7 +2316,8 @@ static int kswapd(void *p)
* us from recursively trying to free more memory as we're
* trying to free the first piece of memory in the first place).
*/
- tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
+ task_set_type(tsk, tt_kswapd);
+ tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE;
set_freezable();

order = 0;



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