diff options
| author | Douglas Anderson <dianders@chromium.org> | 2020-05-26 14:20:06 -0700 |
|---|---|---|
| committer | Daniel Thompson <daniel.thompson@linaro.org> | 2020-06-02 15:15:45 +0100 |
| commit | b1350132fef7e1f0ddfd5a985d516a6ed7a329fc (patch) | |
| tree | ab72a18e652011163b2c8800f312d9e9375396a2 /kernel/debug | |
| parent | 1feb48baf2fb2aff02aa734c04a3ba5c3297d2de (diff) | |
| download | lwn-b1350132fef7e1f0ddfd5a985d516a6ed7a329fc.tar.gz lwn-b1350132fef7e1f0ddfd5a985d516a6ed7a329fc.zip | |
kgdb: Don't call the deinit under spinlock
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>
Link: https://lore.kernel.org/r/20200526142001.1.I523dc33f96589cb9956f5679976d402c8cda36fa@changeid
[daniel.thompson@linaro.org: Resolved merge issues by hand]
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Diffstat (limited to 'kernel/debug')
| -rw-r--r-- | kernel/debug/debug_core.c | 5 |
1 files 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); |