kdb: Gid 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@holly.lan

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191109111624.4.Ibc3d982bbeb9e46872d43973ba808cd4c79537c7@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index 4af48ac536259bda11c7cd7de59e0f8f3634c245..3de0cc780c164aea5c5fd4cf49cabe5795157734 100644 (file)
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/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 {

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 4d44b37468361713fa6b90ddc9413f586403c298..ba12e9f4661ec5a8bcba4e1ec81c15df12ccef58 100644 (file)
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1138,7 +1138,7 @@ static void kdb_dumpregs(struct pt_regs *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;
 

diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index e829b22f3946f0fb78c3b7e1a8b3a46090c9a22e..2e296e4a234ca2925529158d187d6daa5bde4735 100644 (file)
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -240,7 +240,6 @@ extern void *debug_kmalloc(size_t size, gfp_t flags);
 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;