diff options
| author | Sumit Garg <sumit.garg@linaro.org> | 2020-06-04 13:01:18 +0300 |
|---|---|---|
| committer | Daniel Thompson <daniel.thompson@linaro.org> | 2020-06-25 14:04:30 +0300 |
| commit | 2a78b85b70f9c3d450619d369d349ba861320510 (patch) | |
| tree | 72e6d16d654de42d03100d53b9a86eb54e3994ea | |
| parent | e8857288bb620d594c94a219148d18562e52b06e (diff) | |
| download | linux-2a78b85b70f9c3d450619d369d349ba861320510.tar.xz | |
kdb: Make kdb_printf() console handling more robust
While rounding up CPUs via NMIs, its possible that a rounded up CPU
maybe holding a console port lock leading to kgdb master CPU stuck in
a deadlock during invocation of console write operations. A similar
deadlock could also be possible while using synchronous breakpoints.
So in order to avoid such a deadlock, set oops_in_progress to encourage
the console drivers to disregard their internal spin locks: in the
current calling context the risk of deadlock is a bigger problem than
risks due to re-entering the console driver. We operate directly on
oops_in_progress rather than using bust_spinlocks() because the calls
bust_spinlocks() makes on exit are not appropriate for this calling
context.
Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/1591264879-25920-4-git-send-email-sumit.garg@linaro.org
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
| -rw-r--r-- | kernel/debug/kdb/kdb_io.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 58b7d256d0a4..0e4f2eda96d8 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -562,7 +562,18 @@ static void kdb_msg_write(const char *msg, int msg_len) for_each_console(c) { if (!(c->flags & CON_ENABLED)) continue; + /* + * Set oops_in_progress to encourage the console drivers to + * disregard their internal spin locks: in the current calling + * context the risk of deadlock is a bigger problem than risks + * due to re-entering the console driver. We operate directly on + * oops_in_progress rather than using bust_spinlocks() because + * the calls bust_spinlocks() makes on exit are not appropriate + * for this calling context. + */ + ++oops_in_progress; c->write(c, msg, msg_len); + --oops_in_progress; touch_nmi_watchdog(); } } |