[6/7] dyndbg: add locking around zpool-add loop in zpool-init
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Message ID 20201125193626.2266995-7-jim.cromie@gmail.com
State New, archived
Headers show
  • [1/7] dyndbg: move struct _ddebug's display fields to new _ddebug_callsite
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Commit Message

Jim Cromie Nov. 25, 2020, 7:36 p.m. UTC
This commit doesnt improve things, last commit was working, next one
still breaks, despite this "fix".  I keep it separate to isolate it
and the reasoning for review, which now stated, will be refuted as
needed. ;-)

Locking review:

ddebug_zpool_init(), like other ddebug_*_init() routines, does no
locking itself.  Unlike them, it runs later, at late_init.  This patch
doesnt fix the kernel panic that HEAD+1 does.

ddebug_callsite_get/put() are called as a pair under mutex-lock for
all 3 callsite users.

2 of them; ddebug_change() and dynamic_emit_prefix(), do their own
ABBA-ish LGPU (Lock-Get-Put-Unlock).

ddebug_proc_show() does the GP part, and is wrapped by
ddebug_proc_start|stop() with LU.

ddebug_add_module() does LU to protect list_add(), HEAD~1 added
ddebug_zpool_add() loop inside that protection.

This commit adds locking to ddebug_zpool_init(), around the loop of
ddebug_zpool_add(), to match the locking in ddebug_add_module().

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
 lib/dynamic_debug.c | 2 ++
 1 file changed, 2 insertions(+)

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diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 473406b069a7..534d73e45844 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1195,8 +1195,10 @@  static void __init ddebug_zpool_init(void)
 	/* add-module normally does this, but not in time for builtins */
+	mutex_lock(&ddebug_lock);
 	for (iter = __start___dyndbg; iter < __stop___dyndbg; iter++)
+	mutex_unlock(&ddebug_lock);
 	v2pr_info("total pages: %lu compaction: %lu\n",