The patch titled
Subject: kdb: get rid of implicit setting of the current task/regs
has been added to the -mm tree. Its filename is
kdb-gid-rid-of-implicit-setting-of-the-current-task-regs.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kdb-gid-rid-of-implicit-setting-of-the-current-task-regs.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kdb-gid-rid-of-implicit-setting-of-the-current-task-regs.patch
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------------------------------------------------------
From: Douglas Anderson <dianders@xxxxxxxxxxxx>
Subject: kdb: get rid of implicit setting of the current task/regs
Some (but not all?) of the kdb backtrace paths would cause the
kdb_current_task and kdb_current_regs to remain changed. As discussed in
a review of a previous patch [1], this doesn't seem intuitive, so let's
fix that.
...but, it turns out that there's actually no longer any reason to set the
current task / current regs while backtracing anymore anyway. As of
commit 2277b492582d ("kdb: Fix stack crawling on 'running' CPUs that
aren't the master") if we're backtracing on a task running on a CPU we ask
that CPU to do the backtrace itself. Linux can do that without anything
fancy. If we're doing backtrace on a sleeping task we can also do that
fine without updating globals. So this patch mostly just turns into
deleting a bunch of code.
[1] https://lore.kernel.org/r/20191010150735.dhrj3pbjgmjrdpwr@xxxxxxxxx
Link: http://lkml.kernel.org/r/20191109111624.4.Ibc3d982bbeb9e46872d43973ba808cd4c79537c7@changeid
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Cc: Chong Qiao <qiaochong@xxxxxxxxxxx>
Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: James Hogan <jhogan@xxxxxxxxxx>
Cc: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxx>
Cc: Philippe Mathieu-Daud <f4bug@xxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Serge Semin <fancer.lancer@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/debug/kdb/kdb_bt.c | 8 +-------
kernel/debug/kdb/kdb_main.c | 2 +-
kernel/debug/kdb/kdb_private.h | 1 -
3 files changed, 2 insertions(+), 9 deletions(-)
--- a/kernel/debug/kdb/kdb_bt.c~kdb-gid-rid-of-implicit-setting-of-the-current-task-regs
+++ a/kernel/debug/kdb/kdb_bt.c
@@ -119,7 +119,6 @@ kdb_bt_cpu(unsigned long cpu)
return;
}
- kdb_set_current_task(kdb_tsk);
kdb_bt1(kdb_tsk, ~0UL, false);
}
@@ -166,10 +165,8 @@ kdb_bt(int argc, const char **argv)
if (diag)
return diag;
p = find_task_by_pid_ns(pid, &init_pid_ns);
- if (p) {
- kdb_set_current_task(p);
+ if (p)
return kdb_bt1(p, ~0UL, false);
- }
kdb_printf("No process with pid == %ld found\n", pid);
return 0;
} else if (strcmp(argv[0], "btt") == 0) {
@@ -178,11 +175,9 @@ kdb_bt(int argc, const char **argv)
diag = kdbgetularg((char *)argv[1], &addr);
if (diag)
return diag;
- kdb_set_current_task((struct task_struct *)addr);
return kdb_bt1((struct task_struct *)addr, ~0UL, false);
} else if (strcmp(argv[0], "btc") == 0) {
unsigned long cpu = ~0;
- struct task_struct *save_current_task = kdb_current_task;
if (argc > 1)
return KDB_ARGCOUNT;
if (argc == 1) {
@@ -204,7 +199,6 @@ kdb_bt(int argc, const char **argv)
kdb_bt_cpu(cpu);
touch_nmi_watchdog();
}
- kdb_set_current_task(save_current_task);
}
return 0;
} else {
--- a/kernel/debug/kdb/kdb_main.c~kdb-gid-rid-of-implicit-setting-of-the-current-task-regs
+++ a/kernel/debug/kdb/kdb_main.c
@@ -1138,7 +1138,7 @@ static void kdb_dumpregs(struct pt_regs
console_loglevel = old_lvl;
}
-void kdb_set_current_task(struct task_struct *p)
+static void kdb_set_current_task(struct task_struct *p)
{
kdb_current_task = p;
--- a/kernel/debug/kdb/kdb_private.h~kdb-gid-rid-of-implicit-setting-of-the-current-task-regs
+++ a/kernel/debug/kdb/kdb_private.h
@@ -240,7 +240,6 @@ extern void *debug_kmalloc(size_t size,
extern void debug_kfree(void *);
extern void debug_kusage(void);
-extern void kdb_set_current_task(struct task_struct *);
extern struct task_struct *kdb_current_task;
extern struct pt_regs *kdb_current_regs;
_
Patches currently in -mm which might be from dianders@xxxxxxxxxxxx are
mips-kdb-remove-old-workaround-for-backtracing-on-other-cpus.patch
kdb-kdb_current_regs-should-be-private.patch
kdb-kdb_current_task-shouldnt-be-exported.patch
kdb-gid-rid-of-implicit-setting-of-the-current-task-regs.patch
kdb-get-rid-of-confusing-diag-msg-from-rd-if-current-task-has-no-regs.patch
