[PATCH -next] kdb: Use newer api for tasklist scanning

[PATCH -next] kdb: Use newer api for tasklist scanning

[Davidlohr Bueso]

This kills the custom kdb_do_each_thread/kdb_while_each_thread
calls used in kdb to iterate through all tasks. It is obsolete
and racy to use tsk->thread_group, although in this particular
case there is no concurrency so it doesn't matter. Still, lets
trivially replace it for the newer one, maintaining semantics,
of course.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 kernel/debug/kdb/kdb_bt.c      | 4 ++--
 kernel/debug/kdb/kdb_main.c    | 8 ++++----
 kernel/debug/kdb/kdb_private.h | 4 ----
 3 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index 18e03aba2cfc..1f9f0e47aeda 100644
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/kernel/debug/kdb/kdb_bt.c
@@ -149,14 +149,14 @@ kdb_bt(int argc, const char **argv)
 				return 0;
 		}
 		/* Now the inactive tasks */
-		kdb_do_each_thread(g, p) {
+		for_each_process_thread(g, p) {
 			if (KDB_FLAG(CMD_INTERRUPT))
 				return 0;
 			if (task_curr(p))
 				continue;
 			if (kdb_bt1(p, mask, btaprompt))
 				return 0;
-		} kdb_while_each_thread(g, p);
+		}
 	} else if (strcmp(argv[0], "btp") == 0) {
 		struct task_struct *p;
 		unsigned long pid;
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 5c7949061671..930ac1b25ec7 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2299,10 +2299,10 @@ void kdb_ps_suppressed(void)
 		if (kdb_task_state(p, mask_I))
 			++idle;
 	}
-	kdb_do_each_thread(g, p) {
+	for_each_process_thread(g, p) {
 		if (kdb_task_state(p, mask_M))
 			++daemon;
-	} kdb_while_each_thread(g, p);
+	}
 	if (idle || daemon) {
 		if (idle)
 			kdb_printf("%d idle process%s (state I)%s\n",
@@ -2370,12 +2370,12 @@ static int kdb_ps(int argc, const char **argv)
 	}
 	kdb_printf("\n");
 	/* Now the real tasks */
-	kdb_do_each_thread(g, p) {
+	for_each_process_thread(g, p) {
 		if (KDB_FLAG(CMD_INTERRUPT))
 			return 0;
 		if (kdb_task_state(p, mask))
 			kdb_ps1(p);
-	} kdb_while_each_thread(g, p);
+	}
 
 	return 0;
 }
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 2e296e4a234c..a4281fb99299 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -230,10 +230,6 @@ extern struct task_struct *kdb_curr_task(int);
 
 #define kdb_task_has_cpu(p) (task_curr(p))
 
-/* Simplify coexistence with NPTL */
-#define	kdb_do_each_thread(g, p) do_each_thread(g, p)
-#define	kdb_while_each_thread(g, p) while_each_thread(g, p)
-
 #define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
 
 extern void *debug_kmalloc(size_t size, gfp_t flags);
-- 
2.26.2

Re: [PATCH -next] kdb: Use newer api for tasklist scanning

[Oleg Nesterov]

On 08/31, Davidlohr Bueso wrote:
>
> This kills the custom kdb_do_each_thread/kdb_while_each_thread
> calls used in kdb to iterate through all tasks. It is obsolete
> and racy to use tsk->thread_group, although in this particular
> case there is no concurrency so it doesn't matter. Still, lets
> trivially replace it for the newer one, maintaining semantics,
> of course.
>
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> ---
>  kernel/debug/kdb/kdb_bt.c      | 4 ++--
>  kernel/debug/kdb/kdb_main.c    | 8 ++++----
>  kernel/debug/kdb/kdb_private.h | 4 ----
>  3 files changed, 6 insertions(+), 10 deletions(-)

Acked-by: Oleg Nesterov <oleg@redhat.com>

Re: [PATCH -next] kdb: Use newer api for tasklist scanning

[Daniel Thompson]

On Mon, Aug 31, 2020 at 12:34:35PM -0700, Davidlohr Bueso wrote:
> This kills the custom kdb_do_each_thread/kdb_while_each_thread
> calls used in kdb to iterate through all tasks. It is obsolete
> and racy to use tsk->thread_group, although in this particular

No objections to the change but kdb doesn't use tsk->thread_group,
it uses do_each_thread/while_each_thread. Can we change this to
say that is osbsolete and racy to use while_each_thread() (that's
pretty much what the description of the patch that introduced
for_each_thread said)?

Additionally the debug_core uses do_each_thread/while_each_thread.
Presumably that would like to be changed as well?


Daniel.



> case there is no concurrency so it doesn't matter. Still, lets
> trivially replace it for the newer one, maintaining semantics,
> of course.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> ---
>  kernel/debug/kdb/kdb_bt.c      | 4 ++--
>  kernel/debug/kdb/kdb_main.c    | 8 ++++----
>  kernel/debug/kdb/kdb_private.h | 4 ----
>  3 files changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
> index 18e03aba2cfc..1f9f0e47aeda 100644
> --- a/kernel/debug/kdb/kdb_bt.c
> +++ b/kernel/debug/kdb/kdb_bt.c
> @@ -149,14 +149,14 @@ kdb_bt(int argc, const char **argv)
>  				return 0;
>  		}
>  		/* Now the inactive tasks */
> -		kdb_do_each_thread(g, p) {
> +		for_each_process_thread(g, p) {
>  			if (KDB_FLAG(CMD_INTERRUPT))
>  				return 0;
>  			if (task_curr(p))
>  				continue;
>  			if (kdb_bt1(p, mask, btaprompt))
>  				return 0;
> -		} kdb_while_each_thread(g, p);
> +		}
>  	} else if (strcmp(argv[0], "btp") == 0) {
>  		struct task_struct *p;
>  		unsigned long pid;
> diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
> index 5c7949061671..930ac1b25ec7 100644
> --- a/kernel/debug/kdb/kdb_main.c
> +++ b/kernel/debug/kdb/kdb_main.c
> @@ -2299,10 +2299,10 @@ void kdb_ps_suppressed(void)
>  		if (kdb_task_state(p, mask_I))
>  			++idle;
>  	}
> -	kdb_do_each_thread(g, p) {
> +	for_each_process_thread(g, p) {
>  		if (kdb_task_state(p, mask_M))
>  			++daemon;
> -	} kdb_while_each_thread(g, p);
> +	}
>  	if (idle || daemon) {
>  		if (idle)
>  			kdb_printf("%d idle process%s (state I)%s\n",
> @@ -2370,12 +2370,12 @@ static int kdb_ps(int argc, const char **argv)
>  	}
>  	kdb_printf("\n");
>  	/* Now the real tasks */
> -	kdb_do_each_thread(g, p) {
> +	for_each_process_thread(g, p) {
>  		if (KDB_FLAG(CMD_INTERRUPT))
>  			return 0;
>  		if (kdb_task_state(p, mask))
>  			kdb_ps1(p);
> -	} kdb_while_each_thread(g, p);
> +	}
>  
>  	return 0;
>  }
> diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
> index 2e296e4a234c..a4281fb99299 100644
> --- a/kernel/debug/kdb/kdb_private.h
> +++ b/kernel/debug/kdb/kdb_private.h
> @@ -230,10 +230,6 @@ extern struct task_struct *kdb_curr_task(int);
>  
>  #define kdb_task_has_cpu(p) (task_curr(p))
>  
> -/* Simplify coexistence with NPTL */
> -#define	kdb_do_each_thread(g, p) do_each_thread(g, p)
> -#define	kdb_while_each_thread(g, p) while_each_thread(g, p)
> -
>  #define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
>  
>  extern void *debug_kmalloc(size_t size, gfp_t flags);
> -- 
> 2.26.2

Re: [PATCH -next] kdb: Use newer api for tasklist scanning

[Davidlohr Bueso]

On Mon, 07 Sep 2020, Daniel Thompson wrote:

>No objections to the change but kdb doesn't use tsk->thread_group,
>it uses do_each_thread/while_each_thread. Can we change this to
>say that is osbsolete and racy to use while_each_thread() (that's
>pretty much what the description of the patch that introduced
>for_each_thread said)?

Well while_each_thread() is just a loop around next_thread(),
which uses tsk->thread_group. But sure, I can rephrase a v2 to say
while_each_thread.

>
>Additionally the debug_core uses do_each_thread/while_each_thread.
>Presumably that would like to be changed as well?

Are you referring to gdb_cmd_query()? Yeah, that's another one that
can be replaced. Because we need not worry about races, it's rather
simple to justify both replacements in the same patch, which I'll
add to v2.

Thanks,
Davidlohr

[PATCH v2] kdb: Use newer api for tasklist scanning

[Davidlohr Bueso]

This kills using the do_each_thread/while_each_thread combo to
iterate all threads and uses for_each_process_thread() instead,
maintaining semantics. while_each_thread() is ultimately racy
and deprecated;  although in this particular case there is no
concurrency so it doesn't matter. Still lets trivially get rid
of two more users.

Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 kernel/debug/gdbstub.c         | 4 ++--
 kernel/debug/kdb/kdb_bt.c      | 4 ++--
 kernel/debug/kdb/kdb_main.c    | 8 ++++----
 kernel/debug/kdb/kdb_private.h | 4 ----
 4 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
index cc3c43dfec44..b52ebff09ac8 100644
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -725,7 +725,7 @@ static void gdb_cmd_query(struct kgdb_state *ks)
 			}
 		}
 
-		do_each_thread(g, p) {
+		for_each_process_thread(g, p) {
 			if (i >= ks->thr_query && !finished) {
 				int_to_threadref(thref, p->pid);
 				ptr = pack_threadid(ptr, thref);
@@ -735,7 +735,7 @@ static void gdb_cmd_query(struct kgdb_state *ks)
 					finished = 1;
 			}
 			i++;
-		} while_each_thread(g, p);
+		}
 
 		*(--ptr) = '\0';
 		break;
diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index 18e03aba2cfc..1f9f0e47aeda 100644
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/kernel/debug/kdb/kdb_bt.c
@@ -149,14 +149,14 @@ kdb_bt(int argc, const char **argv)
 				return 0;
 		}
 		/* Now the inactive tasks */
-		kdb_do_each_thread(g, p) {
+		for_each_process_thread(g, p) {
 			if (KDB_FLAG(CMD_INTERRUPT))
 				return 0;
 			if (task_curr(p))
 				continue;
 			if (kdb_bt1(p, mask, btaprompt))
 				return 0;
-		} kdb_while_each_thread(g, p);
+		}
 	} else if (strcmp(argv[0], "btp") == 0) {
 		struct task_struct *p;
 		unsigned long pid;
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 5c7949061671..930ac1b25ec7 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2299,10 +2299,10 @@ void kdb_ps_suppressed(void)
 		if (kdb_task_state(p, mask_I))
 			++idle;
 	}
-	kdb_do_each_thread(g, p) {
+	for_each_process_thread(g, p) {
 		if (kdb_task_state(p, mask_M))
 			++daemon;
-	} kdb_while_each_thread(g, p);
+	}
 	if (idle || daemon) {
 		if (idle)
 			kdb_printf("%d idle process%s (state I)%s\n",
@@ -2370,12 +2370,12 @@ static int kdb_ps(int argc, const char **argv)
 	}
 	kdb_printf("\n");
 	/* Now the real tasks */
-	kdb_do_each_thread(g, p) {
+	for_each_process_thread(g, p) {
 		if (KDB_FLAG(CMD_INTERRUPT))
 			return 0;
 		if (kdb_task_state(p, mask))
 			kdb_ps1(p);
-	} kdb_while_each_thread(g, p);
+	}
 
 	return 0;
 }
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 2e296e4a234c..a4281fb99299 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -230,10 +230,6 @@ extern struct task_struct *kdb_curr_task(int);
 
 #define kdb_task_has_cpu(p) (task_curr(p))
 
-/* Simplify coexistence with NPTL */
-#define	kdb_do_each_thread(g, p) do_each_thread(g, p)
-#define	kdb_while_each_thread(g, p) while_each_thread(g, p)
-
 #define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
 
 extern void *debug_kmalloc(size_t size, gfp_t flags);
-- 
2.26.2

Re: [PATCH v2] kdb: Use newer api for tasklist scanning

[Daniel Thompson]

On Mon, Sep 07, 2020 at 01:32:06PM -0700, Davidlohr Bueso wrote:
> This kills using the do_each_thread/while_each_thread combo to
> iterate all threads and uses for_each_process_thread() instead,
> maintaining semantics. while_each_thread() is ultimately racy
> and deprecated;  although in this particular case there is no
> concurrency so it doesn't matter. Still lets trivially get rid
> of two more users.
> 
> Acked-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

Applied. Thanks!


Daniel.


> ---
>  kernel/debug/gdbstub.c         | 4 ++--
>  kernel/debug/kdb/kdb_bt.c      | 4 ++--
>  kernel/debug/kdb/kdb_main.c    | 8 ++++----
>  kernel/debug/kdb/kdb_private.h | 4 ----
>  4 files changed, 8 insertions(+), 12 deletions(-)
> 
> diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
> index cc3c43dfec44..b52ebff09ac8 100644
> --- a/kernel/debug/gdbstub.c
> +++ b/kernel/debug/gdbstub.c
> @@ -725,7 +725,7 @@ static void gdb_cmd_query(struct kgdb_state *ks)
>  			}
>  		}
>  
> -		do_each_thread(g, p) {
> +		for_each_process_thread(g, p) {
>  			if (i >= ks->thr_query && !finished) {
>  				int_to_threadref(thref, p->pid);
>  				ptr = pack_threadid(ptr, thref);
> @@ -735,7 +735,7 @@ static void gdb_cmd_query(struct kgdb_state *ks)
>  					finished = 1;
>  			}
>  			i++;
> -		} while_each_thread(g, p);
> +		}
>  
>  		*(--ptr) = '\0';
>  		break;
> diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
> index 18e03aba2cfc..1f9f0e47aeda 100644
> --- a/kernel/debug/kdb/kdb_bt.c
> +++ b/kernel/debug/kdb/kdb_bt.c
> @@ -149,14 +149,14 @@ kdb_bt(int argc, const char **argv)
>  				return 0;
>  		}
>  		/* Now the inactive tasks */
> -		kdb_do_each_thread(g, p) {
> +		for_each_process_thread(g, p) {
>  			if (KDB_FLAG(CMD_INTERRUPT))
>  				return 0;
>  			if (task_curr(p))
>  				continue;
>  			if (kdb_bt1(p, mask, btaprompt))
>  				return 0;
> -		} kdb_while_each_thread(g, p);
> +		}
>  	} else if (strcmp(argv[0], "btp") == 0) {
>  		struct task_struct *p;
>  		unsigned long pid;
> diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
> index 5c7949061671..930ac1b25ec7 100644
> --- a/kernel/debug/kdb/kdb_main.c
> +++ b/kernel/debug/kdb/kdb_main.c
> @@ -2299,10 +2299,10 @@ void kdb_ps_suppressed(void)
>  		if (kdb_task_state(p, mask_I))
>  			++idle;
>  	}
> -	kdb_do_each_thread(g, p) {
> +	for_each_process_thread(g, p) {
>  		if (kdb_task_state(p, mask_M))
>  			++daemon;
> -	} kdb_while_each_thread(g, p);
> +	}
>  	if (idle || daemon) {
>  		if (idle)
>  			kdb_printf("%d idle process%s (state I)%s\n",
> @@ -2370,12 +2370,12 @@ static int kdb_ps(int argc, const char **argv)
>  	}
>  	kdb_printf("\n");
>  	/* Now the real tasks */
> -	kdb_do_each_thread(g, p) {
> +	for_each_process_thread(g, p) {
>  		if (KDB_FLAG(CMD_INTERRUPT))
>  			return 0;
>  		if (kdb_task_state(p, mask))
>  			kdb_ps1(p);
> -	} kdb_while_each_thread(g, p);
> +	}
>  
>  	return 0;
>  }
> diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
> index 2e296e4a234c..a4281fb99299 100644
> --- a/kernel/debug/kdb/kdb_private.h
> +++ b/kernel/debug/kdb/kdb_private.h
> @@ -230,10 +230,6 @@ extern struct task_struct *kdb_curr_task(int);
>  
>  #define kdb_task_has_cpu(p) (task_curr(p))
>  
> -/* Simplify coexistence with NPTL */
> -#define	kdb_do_each_thread(g, p) do_each_thread(g, p)
> -#define	kdb_while_each_thread(g, p) while_each_thread(g, p)
> -
>  #define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
>  
>  extern void *debug_kmalloc(size_t size, gfp_t flags);
> -- 
> 2.26.2