Commit 29fc5f93 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Force DEFAULT_RCU_BLIMIT to 1000 for strict RCU GPs 



The value of DEFAULT_RCU_BLIMIT is normally set to 10, the idea being to
avoid needless response-time degradation due to RCU callback invocation.
However, when CONFIG_RCU_STRICT_GRACE_PERIOD=y it is better to avoid
throttling callback execution in order to better detect pointer
leaks from RCU read-side critical sections.  This commit therefore
sets the value of DEFAULT_RCU_BLIMIT to 1000 in kernels built with
CONFIG_RCU_STRICT_GRACE_PERIOD=y.

Reported-by Jann Horn <jannh@google.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent aecd34b9

kernel/rcu/tree.c

+7 −6
Original line number Diff line number Diff line
@@ -468,17 +468,18 @@ static int rcu_is_cpu_rrupt_from_idle(void) 
	return __this_cpu_read(rcu_data.dynticks_nesting) == 0;

}



#define DEFAULT_RCU_BLIMIT 10     /* Maximum callbacks per rcu_do_batch ... */

#define DEFAULT_MAX_RCU_BLIMIT 10000 /* ... even during callback flood. */

#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)

				// Maximum callbacks per rcu_do_batch ...

#define DEFAULT_MAX_RCU_BLIMIT 10000 // ... even during callback flood.

static long blimit = DEFAULT_RCU_BLIMIT;

#define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */

#define DEFAULT_RCU_QHIMARK 10000 // If this many pending, ignore blimit.

static long qhimark = DEFAULT_RCU_QHIMARK;

#define DEFAULT_RCU_QLOMARK 100   /* Once only this many pending, use blimit. */

#define DEFAULT_RCU_QLOMARK 100   // Once only this many pending, use blimit.

static long qlowmark = DEFAULT_RCU_QLOMARK;

#define DEFAULT_RCU_QOVLD_MULT 2

#define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK)

static long qovld = DEFAULT_RCU_QOVLD; /* If this many pending, hammer QS. */

static long qovld_calc = -1;	  /* No pre-initialization lock acquisitions! */

static long qovld = DEFAULT_RCU_QOVLD; // If this many pending, hammer QS.

static long qovld_calc = -1;	  // No pre-initialization lock acquisitions!



module_param(blimit, long, 0444);

module_param(qhimark, long, 0444);

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