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sched: Add wrapper for get_wchan() to keep task blocked

Browse Source 
Having a stable wchan means the process must be blocked and for it to
stay that way while performing stack unwinding.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> [arm]
Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64]
Link: https://lkml.kernel.org/r/20211008111626.332092234@infradead.org
This commit is contained in:
Kees Cook 2021-09-29 15:02:14 -07:00 committed by Peter Zijlstra
parent bc9bbb8173
commit 42a20f86dc
50 changed files with 80 additions and 112 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/alpha/include/asm/processor.h
View File

@ -42,7 +42,7 @@ extern void start_thread(struct pt_regs *, unsigned long, unsigned long);
struct task_struct;
extern void release_thread(struct task_struct *);
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) (task_pt_regs(tsk)->pc)

5
arch/alpha/kernel/process.c
View File

@ -376,12 +376,11 @@ thread_saved_pc(struct task_struct *t)
}
unsigned long
get_wchan(struct task_struct *p)
__get_wchan(struct task_struct *p)
{
unsigned long schedule_frame;
unsigned long pc;
if (!p || p == current || task_is_running(p))
return 0;
/*
* This one depends on the frame size of schedule(). Do a
* "disass schedule" in gdb to find the frame size. Also, the

2
arch/arc/include/asm/processor.h
View File

@ -70,7 +70,7 @@ struct task_struct;
extern void start_thread(struct pt_regs * regs, unsigned long pc,
unsigned long usp);
extern unsigned int get_wchan(struct task_struct *p);
extern unsigned int __get_wchan(struct task_struct *p);
#endif /* !__ASSEMBLY__ */

4
arch/arc/kernel/stacktrace.c
View File

@ -15,7 +15,7 @@
* = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
*
* vineetg: March 2009
* -Implemented correct versions of thread_saved_pc() and get_wchan()
* -Implemented correct versions of thread_saved_pc() and __get_wchan()
*
* rajeshwarr: 2008
* -Initial implementation
@ -248,7 +248,7 @@ void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
* Of course just returning schedule( ) would be pointless so unwind until
* the function is not in schedular code
*/
unsigned int get_wchan(struct task_struct *tsk)
unsigned int __get_wchan(struct task_struct *tsk)
{
return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
}

2
arch/arm/include/asm/processor.h
View File

@ -84,7 +84,7 @@ struct task_struct;
/* Free all resources held by a thread. */
extern void release_thread(struct task_struct *);
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define task_pt_regs(p) \
((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1)

4
arch/arm/kernel/process.c
View File

@ -276,13 +276,11 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
return 0;
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
struct stackframe frame;
unsigned long stack_page;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
frame.fp = thread_saved_fp(p);
frame.sp = thread_saved_sp(p);

2
arch/arm64/include/asm/processor.h
View File

@ -257,7 +257,7 @@ struct task_struct;
/* Free all resources held by a thread. */
extern void release_thread(struct task_struct *);
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
void update_sctlr_el1(u64 sctlr);

4
arch/arm64/kernel/process.c
View File

@ -528,13 +528,11 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
return last;
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
struct stackframe frame;
unsigned long stack_page, ret = 0;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
stack_page = (unsigned long)try_get_task_stack(p);
if (!stack_page)

2
arch/csky/include/asm/processor.h
View File

@ -81,7 +81,7 @@ static inline void release_thread(struct task_struct *dead_task)
extern int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) (task_pt_regs(tsk)->pc)
#define KSTK_ESP(tsk) (task_pt_regs(tsk)->usp)

5
arch/csky/kernel/stacktrace.c
View File

@ -111,12 +111,11 @@ static bool save_wchan(unsigned long pc, void *arg)
return false;
}
unsigned long get_wchan(struct task_struct *task)
unsigned long __get_wchan(struct task_struct *task)
{
unsigned long pc = 0;
if (likely(task && task != current && !task_is_running(task)))
walk_stackframe(task, NULL, save_wchan, &pc);
walk_stackframe(task, NULL, save_wchan, &pc);
return pc;
}

2
arch/h8300/include/asm/processor.h
View File

@ -105,7 +105,7 @@ static inline void release_thread(struct task_struct *dead_task)
{
}
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) \
({ \

5
arch/h8300/kernel/process.c
View File

@ -128,15 +128,12 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
return 0;
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long fp, pc;
unsigned long stack_page;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
stack_page = (unsigned long)p;
fp = ((struct pt_regs *)p->thread.ksp)->er6;
do {

2
arch/hexagon/include/asm/processor.h
View File

@ -64,7 +64,7 @@ struct thread_struct {
extern void release_thread(struct task_struct *dead_task);
/* Get wait channel for task P. */
extern unsigned long get_wchan(struct task_struct *p);
extern unsigned long __get_wchan(struct task_struct *p);
/* The following stuff is pretty HEXAGON specific. */

4
arch/hexagon/kernel/process.c
View File

@ -130,13 +130,11 @@ void flush_thread(void)
* is an identification of the point at which the scheduler
* was invoked by a blocked thread.
*/
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long fp, pc;
unsigned long stack_page;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
stack_page = (unsigned long)task_stack_page(p);
fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;

2
arch/ia64/include/asm/processor.h
View File

@ -330,7 +330,7 @@ struct task_struct;
#define release_thread(dead_task)
/* Get wait channel for task P. */
extern unsigned long get_wchan (struct task_struct *p);
extern unsigned long __get_wchan (struct task_struct *p);
/* Return instruction pointer of blocked task TSK. */
#define KSTK_EIP(tsk) \

5
arch/ia64/kernel/process.c
View File

@ -523,15 +523,12 @@ exit_thread (struct task_struct *tsk)
}
unsigned long
get_wchan (struct task_struct *p)
__get_wchan (struct task_struct *p)
{
struct unw_frame_info info;
unsigned long ip;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
/*
* Note: p may not be a blocked task (it could be current or
* another process running on some other CPU. Rather than

2
arch/m68k/include/asm/processor.h
View File

@ -150,7 +150,7 @@ static inline void release_thread(struct task_struct *dead_task)
{
}
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) \
({ \

4
arch/m68k/kernel/process.c
View File

@ -263,13 +263,11 @@ int dump_fpu (struct pt_regs *regs, struct user_m68kfp_struct *fpu)
}
EXPORT_SYMBOL(dump_fpu);
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long fp, pc;
unsigned long stack_page;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
stack_page = (unsigned long)task_stack_page(p);
fp = ((struct switch_stack *)p->thread.ksp)->a6;

2
arch/microblaze/include/asm/processor.h
View File

@ -68,7 +68,7 @@ static inline void release_thread(struct task_struct *dead_task)
{
}
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
/* The size allocated for kernel stacks. This _must_ be a power of two! */
# define KERNEL_STACK_SIZE 0x2000

2
arch/microblaze/kernel/process.c
View File

@ -112,7 +112,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
return 0;
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
/* TBD (used by procfs) */
return 0;

2
arch/mips/include/asm/processor.h
View File

@ -369,7 +369,7 @@ static inline void flush_thread(void)
{
}
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define __KSTK_TOS(tsk) ((unsigned long)task_stack_page(tsk) + \
THREAD_SIZE - 32 - sizeof(struct pt_regs))

8
arch/mips/kernel/process.c
View File

@ -511,7 +511,7 @@ static int __init frame_info_init(void)
/*
* Without schedule() frame info, result given by
* thread_saved_pc() and get_wchan() are not reliable.
* thread_saved_pc() and __get_wchan() are not reliable.
*/
if (schedule_mfi.pc_offset < 0)
printk("Can't analyze schedule() prologue at %p\n", schedule);
@ -652,9 +652,9 @@ unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
#endif
/*
* get_wchan - a maintenance nightmare^W^Wpain in the ass ...
* __get_wchan - a maintenance nightmare^W^Wpain in the ass ...
*/
unsigned long get_wchan(struct task_struct *task)
unsigned long __get_wchan(struct task_struct *task)
{
unsigned long pc = 0;
#ifdef CONFIG_KALLSYMS
@ -662,8 +662,6 @@ unsigned long get_wchan(struct task_struct *task)
unsigned long ra = 0;
#endif
if (!task || task == current || task_is_running(task))
goto out;
if (!task_stack_page(task))
goto out;

2
arch/nds32/include/asm/processor.h
View File

@ -83,7 +83,7 @@ extern struct task_struct *last_task_used_math;
/* Prepare to copy thread state - unlazy all lazy status */
#define prepare_to_copy(tsk) do { } while (0)
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define cpu_relax() barrier()

7
arch/nds32/kernel/process.c
View File

@ -233,15 +233,12 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)
EXPORT_SYMBOL(dump_fpu);
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long fp, lr;
unsigned long stack_start, stack_end;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
if (IS_ENABLED(CONFIG_FRAME_POINTER)) {
stack_start = (unsigned long)end_of_stack(p);
stack_end = (unsigned long)task_stack_page(p) + THREAD_SIZE;
@ -258,5 +255,3 @@ unsigned long get_wchan(struct task_struct *p)
}
return 0;
}
EXPORT_SYMBOL(get_wchan);

2
arch/nios2/include/asm/processor.h
View File

@ -69,7 +69,7 @@ static inline void release_thread(struct task_struct *dead_task)
{
}
extern unsigned long get_wchan(struct task_struct *p);
extern unsigned long __get_wchan(struct task_struct *p);
#define task_pt_regs(p) \
((struct pt_regs *)(THREAD_SIZE + task_stack_page(p)) - 1)

5
arch/nios2/kernel/process.c
View File

@ -217,15 +217,12 @@ void dump(struct pt_regs *fp)
pr_emerg("\n\n");
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long fp, pc;
unsigned long stack_page;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
stack_page = (unsigned long)p;
fp = ((struct switch_stack *)p->thread.ksp)->fp; /* ;dgt2 */
do {

2
arch/openrisc/include/asm/processor.h
View File

@ -73,7 +73,7 @@ struct thread_struct {
void start_thread(struct pt_regs *regs, unsigned long nip, unsigned long sp);
void release_thread(struct task_struct *);
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define cpu_relax() barrier()

2
arch/openrisc/kernel/process.c
View File

@ -263,7 +263,7 @@ void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
dest[35] = 0;
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
/* TODO */

2
arch/parisc/include/asm/processor.h
View File

@ -273,7 +273,7 @@ struct mm_struct;
/* Free all resources held by a thread. */
extern void release_thread(struct task_struct *);
extern unsigned long get_wchan(struct task_struct *p);
extern unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) ((tsk)->thread.regs.iaoq[0])
#define KSTK_ESP(tsk) ((tsk)->thread.regs.gr[30])

5
arch/parisc/kernel/process.c
View File

@ -240,15 +240,12 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
}
unsigned long
get_wchan(struct task_struct *p)
__get_wchan(struct task_struct *p)
{
struct unwind_frame_info info;
unsigned long ip;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
/*
* These bracket the sleeping functions..
*/

2
arch/powerpc/include/asm/processor.h
View File

@ -300,7 +300,7 @@ struct thread_struct {
#define task_pt_regs(tsk) ((tsk)->thread.regs)
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) ((tsk)->thread.regs? (tsk)->thread.regs->nip: 0)
#define KSTK_ESP(tsk) ((tsk)->thread.regs? (tsk)->thread.regs->gpr[1]: 0)

9
arch/powerpc/kernel/process.c
View File

@ -2111,14 +2111,11 @@ int validate_sp(unsigned long sp, struct task_struct *p,
EXPORT_SYMBOL(validate_sp);
static unsigned long __get_wchan(struct task_struct *p)
static unsigned long ___get_wchan(struct task_struct *p)
{
unsigned long ip, sp;
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
sp = p->thread.ksp;
if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD))
return 0;
@ -2137,14 +2134,14 @@ static unsigned long __get_wchan(struct task_struct *p)
return 0;
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long ret;
if (!try_get_task_stack(p))
return 0;
ret = __get_wchan(p);
ret = ___get_wchan(p);
put_task_stack(p);

2
arch/riscv/include/asm/processor.h
View File

@ -66,7 +66,7 @@ static inline void release_thread(struct task_struct *dead_task)
{
}
extern unsigned long get_wchan(struct task_struct *p);
extern unsigned long __get_wchan(struct task_struct *p);
static inline void wait_for_interrupt(void)

12
arch/riscv/kernel/stacktrace.c
View File

@ -128,16 +128,14 @@ static bool save_wchan(void *arg, unsigned long pc)
return true;
}
unsigned long get_wchan(struct task_struct *task)
unsigned long __get_wchan(struct task_struct *task)
{
unsigned long pc = 0;
if (likely(task && task != current && !task_is_running(task))) {
if (!try_get_task_stack(task))
return 0;
walk_stackframe(task, NULL, save_wchan, &pc);
put_task_stack(task);
}
if (!try_get_task_stack(task))
return 0;
walk_stackframe(task, NULL, save_wchan, &pc);
put_task_stack(task);
return pc;
}

2
arch/s390/include/asm/processor.h
View File

@ -192,7 +192,7 @@ static inline void release_thread(struct task_struct *tsk) { }
void guarded_storage_release(struct task_struct *tsk);
void gs_load_bc_cb(struct pt_regs *regs);
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
#define task_pt_regs(tsk) ((struct pt_regs *) \
(task_stack_page(tsk) + THREAD_SIZE) - 1)
#define KSTK_EIP(tsk) (task_pt_regs(tsk)->psw.addr)

4
arch/s390/kernel/process.c
View File

@ -181,12 +181,12 @@ void execve_tail(void)
asm volatile("sfpc %0" : : "d" (0));
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
struct unwind_state state;
unsigned long ip = 0;
if (!p || p == current || task_is_running(p) || !task_stack_page(p))
if (!task_stack_page(p))
return 0;
if (!try_get_task_stack(p))

2
arch/sh/include/asm/processor_32.h
View File

@ -180,7 +180,7 @@ static inline void show_code(struct pt_regs *regs)
}
#endif
extern unsigned long get_wchan(struct task_struct *p);
extern unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) (task_pt_regs(tsk)->pc)
#define KSTK_ESP(tsk) (task_pt_regs(tsk)->regs[15])

5
arch/sh/kernel/process_32.c
View File

@ -182,13 +182,10 @@ __switch_to(struct task_struct *prev, struct task_struct *next)
return prev;
}
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long pc;
if (!p || p == current || task_is_running(p))
return 0;
/*
* The same comment as on the Alpha applies here, too ...
*/

2
arch/sparc/include/asm/processor_32.h
View File

@ -89,7 +89,7 @@ static inline void start_thread(struct pt_regs * regs, unsigned long pc,
/* Free all resources held by a thread. */
#define release_thread(tsk) do { } while(0)
unsigned long get_wchan(struct task_struct *);
unsigned long __get_wchan(struct task_struct *);
#define task_pt_regs(tsk) ((tsk)->thread.kregs)
#define KSTK_EIP(tsk) ((tsk)->thread.kregs->pc)

2
arch/sparc/include/asm/processor_64.h
View File

@ -183,7 +183,7 @@ do { \
/* Free all resources held by a thread. */
#define release_thread(tsk) do { } while (0)
unsigned long get_wchan(struct task_struct *task);
unsigned long __get_wchan(struct task_struct *task);
#define task_pt_regs(tsk) (task_thread_info(tsk)->kregs)
#define KSTK_EIP(tsk) (task_pt_regs(tsk)->tpc)

5
arch/sparc/kernel/process_32.c
View File

@ -365,7 +365,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
return 0;
}
unsigned long get_wchan(struct task_struct *task)
unsigned long __get_wchan(struct task_struct *task)
{
unsigned long pc, fp, bias = 0;
unsigned long task_base = (unsigned long) task;
@ -373,9 +373,6 @@ unsigned long get_wchan(struct task_struct *task)
struct reg_window32 *rw;
int count = 0;
if (!task || task == current || task_is_running(task))
goto out;
fp = task_thread_info(task)->ksp + bias;
do {
/* Bogus frame pointer? */

5
arch/sparc/kernel/process_64.c
View File

@ -663,7 +663,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
return 0;
}
unsigned long get_wchan(struct task_struct *task)
unsigned long __get_wchan(struct task_struct *task)
{
unsigned long pc, fp, bias = 0;
struct thread_info *tp;
@ -671,9 +671,6 @@ unsigned long get_wchan(struct task_struct *task)
unsigned long ret = 0;
int count = 0;
if (!task || task == current || task_is_running(task))
goto out;
tp = task_thread_info(task);
bias = STACK_BIAS;
fp = task_thread_info(task)->ksp + bias;

2
arch/um/include/asm/processor-generic.h
View File

@ -106,6 +106,6 @@ extern struct cpuinfo_um boot_cpu_data;
#define cache_line_size() (boot_cpu_data.cache_alignment)
#define KSTK_REG(tsk, reg) get_thread_reg(reg, &tsk->thread.switch_buf)
extern unsigned long get_wchan(struct task_struct *p);
extern unsigned long __get_wchan(struct task_struct *p);
#endif

5
arch/um/kernel/process.c
View File

@ -364,14 +364,11 @@ unsigned long arch_align_stack(unsigned long sp)
}
#endif
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long stack_page, sp, ip;
bool seen_sched = 0;
if ((p == NULL) || (p == current) || task_is_running(p))
return 0;
stack_page = (unsigned long) task_stack_page(p);
/* Bail if the process has no kernel stack for some reason */
if (stack_page == 0)

2
arch/x86/include/asm/processor.h
View File

@ -589,7 +589,7 @@ static inline void load_sp0(unsigned long sp0)
/* Free all resources held by a thread. */
extern void release_thread(struct task_struct *);
unsigned long get_wchan(struct task_struct *p);
unsigned long __get_wchan(struct task_struct *p);
/*
* Generic CPUID function

5
arch/x86/kernel/process.c
View File

@ -942,13 +942,10 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
* because the task might wake up and we might look at a stack
* changing under us.
*/
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long entry = 0;
if (p == current || task_is_running(p))
return 0;
stack_trace_save_tsk(p, &entry, 1, 0);
return entry;
}

2
arch/xtensa/include/asm/processor.h
View File

@ -215,7 +215,7 @@ struct mm_struct;
/* Free all resources held by a thread. */
#define release_thread(thread) do { } while(0)
extern unsigned long get_wchan(struct task_struct *p);
extern unsigned long __get_wchan(struct task_struct *p);
#define KSTK_EIP(tsk) (task_pt_regs(tsk)->pc)
#define KSTK_ESP(tsk) (task_pt_regs(tsk)->areg[1])

5
arch/xtensa/kernel/process.c
View File

@ -298,15 +298,12 @@ int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
* These bracket the sleeping functions..
*/
unsigned long get_wchan(struct task_struct *p)
unsigned long __get_wchan(struct task_struct *p)
{
unsigned long sp, pc;
unsigned long stack_page = (unsigned long) task_stack_page(p);
int count = 0;
if (!p || p == current || task_is_running(p))
return 0;
sp = p->thread.sp;
pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);

1
include/linux/sched.h
View File

@ -2139,6 +2139,7 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
#endif /* CONFIG_SMP */
extern bool sched_task_on_rq(struct task_struct *p);
extern unsigned long get_wchan(struct task_struct *p);
/*
* In order to reduce various lock holder preemption latencies provide an

19
kernel/sched/core.c
View File

@ -1966,6 +1966,25 @@ bool sched_task_on_rq(struct task_struct *p)
return task_on_rq_queued(p);
}
unsigned long get_wchan(struct task_struct *p)
{
unsigned long ip = 0;
unsigned int state;
if (!p || p == current)
return 0;
/* Only get wchan if task is blocked and we can keep it that way. */
raw_spin_lock_irq(&p->pi_lock);
state = READ_ONCE(p->__state);
smp_rmb(); /* see try_to_wake_up() */
if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq)
ip = __get_wchan(p);
raw_spin_unlock_irq(&p->pi_lock);
return ip;
}
static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
{
if (!(flags & ENQUEUE_NOCLOCK))