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author | Sumit Garg <sumit.garg@linaro.org> | 2020-06-04 15:31:19 +0530 |
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committer | Daniel Thompson <daniel.thompson@linaro.org> | 2020-06-26 15:40:16 +0100 |
commit | 5946d1f5b309381805bad3ddc3054c04f4ae9c24 (patch) | |
tree | cc5d93c6b074be806bd226223ebe4ec4fdca9f2c /kernel/debug/kdb | |
parent | 2a78b85b70f9c3d450619d369d349ba861320510 (diff) | |
download | linux-5946d1f5b309381805bad3ddc3054c04f4ae9c24.tar.bz2 |
kdb: Switch to use safer dbg_io_ops over console APIs
In kgdb context, calling console handlers aren't safe due to locks used
in those handlers which could in turn lead to a deadlock. Although, using
oops_in_progress increases the chance to bypass locks in most console
handlers but it might not be sufficient enough in case a console uses
more locks (VT/TTY is good example).
Currently when a driver provides both polling I/O and a console then kdb
will output using the console. We can increase robustness by using the
currently active polling I/O driver (which should be lockless) instead
of the corresponding console. For several common cases (e.g. an
embedded system with a single serial port that is used both for console
output and debugger I/O) this will result in no console handler being
used.
In order to achieve this we need to reverse the order of preference to
use dbg_io_ops (uses polling I/O mode) over console APIs. So we just
store "struct console" that represents debugger I/O in dbg_io_ops and
while emitting kdb messages, skip console that matches dbg_io_ops
console in order to avoid duplicate messages. After this change,
"is_console" param becomes redundant and hence removed.
Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Link: https://lore.kernel.org/r/1591264879-25920-5-git-send-email-sumit.garg@linaro.org
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Diffstat (limited to 'kernel/debug/kdb')
-rw-r--r-- | kernel/debug/kdb/kdb_io.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 0e4f2eda96d8..683a799618ad 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -549,7 +549,7 @@ static void kdb_msg_write(const char *msg, int msg_len) if (msg_len == 0) return; - if (dbg_io_ops && !dbg_io_ops->is_console) { + if (dbg_io_ops) { const char *cp = msg; int len = msg_len; @@ -562,6 +562,8 @@ static void kdb_msg_write(const char *msg, int msg_len) for_each_console(c) { if (!(c->flags & CON_ENABLED)) continue; + if (c == dbg_io_ops->cons) + continue; /* * Set oops_in_progress to encourage the console drivers to * disregard their internal spin locks: in the current calling |