lkml.org 
[lkml]   [2020]   [May]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] kgdb: Don't call the deinit under spinlock
Date
When I combined kgdboc_earlycon with an inflight patch titled ("soc:
qcom-geni-se: Add interconnect support to fix earlycon crash") [1]
things went boom. Specifically I got a crash during the transition
between kgdboc_earlycon and the main kgdboc that looked like this:

Call trace:
__schedule_bug+0x68/0x6c
__schedule+0x75c/0x924
schedule+0x8c/0xbc
schedule_timeout+0x9c/0xfc
do_wait_for_common+0xd0/0x160
wait_for_completion_timeout+0x54/0x74
rpmh_write_batch+0x1fc/0x23c
qcom_icc_bcm_voter_commit+0x1b4/0x388
qcom_icc_set+0x2c/0x3c
apply_constraints+0x5c/0x98
icc_set_bw+0x204/0x3bc
icc_put+0x30/0xf8
geni_remove_earlycon_icc_vote+0x6c/0x9c
qcom_geni_serial_earlycon_exit+0x10/0x1c
kgdboc_earlycon_deinit+0x38/0x58
kgdb_register_io_module+0x11c/0x194
configure_kgdboc+0x108/0x174
kgdboc_probe+0x38/0x60
platform_drv_probe+0x90/0xb0
really_probe+0x130/0x2fc
...

The problem was that we were holding the "kgdb_registration_lock"
while calling into code that didn't expect to be called in spinlock
context.

Let's slightly defer when we call the deinit code so that it's not
done under spinlock.

NOTE: this does mean that the "deinit" call of the old kgdb IO module
is now made _after_ the init of the new IO module, but presumably
that's OK.

[1] https://lkml.kernel.org/r/1588919619-21355-3-git-send-email-akashast@codeaurora.org

Fixes: 220995622da5 ("kgdboc: Add kgdboc_earlycon to support early kgdb using boot consoles")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

kernel/debug/debug_core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 4d59aa907fdc..ef94e906f05a 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -1089,7 +1089,6 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
}
pr_info("Replacing I/O driver %s with %s\n",
old_dbg_io_ops->name, new_dbg_io_ops->name);
- old_dbg_io_ops->deinit();
}

if (new_dbg_io_ops->init) {
@@ -1104,8 +1103,10 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)

spin_unlock(&kgdb_registration_lock);

- if (old_dbg_io_ops)
+ if (old_dbg_io_ops) {
+ old_dbg_io_ops->deinit();
return 0;
+ }

pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);

--
2.27.0.rc0.183.gde8f92d652-goog
\
 
 \ /
  Last update: 2020-05-26 23:20    [W:0.038 / U:12.568 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site