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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 2277b49258 ("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>
This commit is contained in:
Douglas Anderson 2019-11-09 11:16:43 -08:00 committed by Daniel Thompson
parent a8649fb0a8
commit 9441d5f6b7
3 changed files with 2 additions and 9 deletions
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8
kernel/debug/kdb/kdb_bt.c
View File

@ -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 {

2
kernel/debug/kdb/kdb_main.c
View File

@ -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;

1
kernel/debug/kdb/kdb_private.h
View File

@ -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;