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rcutorture: Make rcutorture_one_extend() check reader state

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This commit adds reader-state debugging checks to a new function named
rcutorture_one_extend_check(), which is invoked before and after setting
new reader states by the existing rcutorture_one_extend() function.
These checks have proven to be rather heavyweight, reducing reproduction
rate of some failures by a factor of two.  They are therefore hidden
behind a new RCU_TORTURE_TEST_CHK_RDR_STATE Kconfig option.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Tested-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
This commit is contained in:
Paul E. McKenney 2024-10-30 17:10:22 -07:00 committed by Uladzislau Rezki (Sony)
parent 16338e7cb7
commit ec9d6356bf
2 changed files with 79 additions and 8 deletions
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16
kernel/rcu/Kconfig.debug
View File

@ -53,6 +53,22 @@ config RCU_TORTURE_TEST
Say M if you want the RCU torture tests to build as a module.
Say N if you are unsure.
config RCU_TORTURE_TEST_CHK_RDR_STATE
tristate "Check rcutorture reader state"
depends on RCU_TORTURE_TEST
default n
help
This option causes rcutorture to check the desired rcutorture
reader state for each segment against the actual context.
Note that PREEMPT_COUNT must be enabled if the preempt-disabled
and bh-disabled checks are to take effect, and that PREEMPT_RCU
must be enabled for the RCU-nesting checks to take effect.
These checks add overhead, and this Kconfig options is therefore
disabled by default.
Say Y here if you want rcutorture reader contexts checked.
Say N if you are unsure.
config RCU_TORTURE_TEST_LOG_CPU
tristate "Log CPU for rcutorture failures"
depends on RCU_TORTURE_TEST

71
kernel/rcu/rcutorture.c
View File

@ -359,7 +359,8 @@ struct rcu_torture_ops {
void (*read_delay)(struct torture_random_state *rrsp,
struct rt_read_seg *rtrsp);
void (*readunlock)(int idx);
int (*readlock_held)(void);
int (*readlock_held)(void); // lockdep.
int (*readlock_nesting)(void); // actual nesting, if available, -1 if not.
unsigned long (*get_gp_seq)(void);
unsigned long (*gp_diff)(unsigned long new, unsigned long old);
void (*deferred_free)(struct rcu_torture *p);
@ -466,6 +467,15 @@ static void rcu_torture_read_unlock(int idx)
rcu_read_unlock();
}
static int rcu_torture_readlock_nesting(void)
{
if (IS_ENABLED(CONFIG_PREEMPT_RCU))
return rcu_preempt_depth();
if (IS_ENABLED(CONFIG_PREEMPT_COUNT))
return (preempt_count() & PREEMPT_MASK);
return -1;
}
/*
* Update callback in the pipe. This should be invoked after a grace period.
*/
@ -555,6 +565,7 @@ static struct rcu_torture_ops rcu_ops = {
.read_delay = rcu_read_delay,
.readunlock = rcu_torture_read_unlock,
.readlock_held = torture_readlock_not_held,
.readlock_nesting = rcu_torture_readlock_nesting,
.get_gp_seq = rcu_get_gp_seq,
.gp_diff = rcu_seq_diff,
.deferred_free = rcu_torture_deferred_free,
@ -1847,6 +1858,44 @@ static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
smp_store_release(&rtrcp_assigner->rtc_chkrdr, -1); // Assigner can again assign.
}
// Verify the specified RCUTORTURE_RDR* state.
#define ROEC_ARGS "%s %s: Current %#x To add %#x To remove %#x\n", __func__, s, curstate, new, old
static void rcutorture_one_extend_check(char *s, int curstate, int new, int old, bool insoftirq)
{
if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE))
return;
WARN_ONCE(!(curstate & RCUTORTURE_RDR_IRQ) && irqs_disabled(), ROEC_ARGS);
WARN_ONCE((curstate & RCUTORTURE_RDR_IRQ) && !irqs_disabled(), ROEC_ARGS);
// If CONFIG_PREEMPT_COUNT=n, further checks are unreliable.
if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
return;
WARN_ONCE((curstate & (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH)) &&
!(preempt_count() & SOFTIRQ_MASK), ROEC_ARGS);
WARN_ONCE((curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) &&
!(preempt_count() & PREEMPT_MASK), ROEC_ARGS);
WARN_ONCE(cur_ops->readlock_nesting &&
(curstate & (RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2)) &&
cur_ops->readlock_nesting() == 0, ROEC_ARGS);
// Timer handlers have all sorts of stuff disabled, so ignore
// unintended disabling.
if (insoftirq)
return;
WARN_ONCE(cur_ops->extendables &&
!(curstate & (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH)) &&
(preempt_count() & SOFTIRQ_MASK), ROEC_ARGS);
WARN_ONCE(cur_ops->extendables &&
!(curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) &&
(preempt_count() & PREEMPT_MASK), ROEC_ARGS);
WARN_ONCE(cur_ops->readlock_nesting &&
!(curstate & (RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2)) &&
cur_ops->readlock_nesting() > 0, ROEC_ARGS);
}
/*
* Do one extension of an RCU read-side critical section using the
* current reader state in readstate (set to zero for initial entry
@ -1856,7 +1905,7 @@ static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
* beginning or end of the critical section and if there was actually a
* change, do a ->read_delay().
*/
static void rcutorture_one_extend(int *readstate, int newstate,
static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
struct torture_random_state *trsp,
struct rt_read_seg *rtrsp)
{
@ -1870,6 +1919,7 @@ static void rcutorture_one_extend(int *readstate, int newstate,
WARN_ON_ONCE(idxold2 < 0);
WARN_ON_ONCE(idxold2 & ~RCUTORTURE_RDR_ALLBITS);
rcutorture_one_extend_check("before change", idxold1, statesnew, statesold, insoftirq);
rtrsp->rt_readstate = newstate;
if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_CPU))
rtrsp->rt_cpu = raw_smp_processor_id();
@ -1890,6 +1940,10 @@ static void rcutorture_one_extend(int *readstate, int newstate,
if (statesnew & RCUTORTURE_RDR_RCU_2)
idxnew2 = (cur_ops->readlock() << RCUTORTURE_RDR_SHIFT_2) & RCUTORTURE_RDR_MASK_2;
// Complain unless both the old and the new protection is in place.
rcutorture_one_extend_check("during change",
idxold1 | statesnew, statesnew, statesold, insoftirq);
/*
* Next, remove old protection, in decreasing order of strength
* to avoid unlock paths that aren't safe in the stronger
@ -1940,6 +1994,7 @@ static void rcutorture_one_extend(int *readstate, int newstate,
WARN_ON_ONCE(*readstate < 0);
if (WARN_ON_ONCE(*readstate & ~RCUTORTURE_RDR_ALLBITS))
pr_info("Unexpected readstate value of %#x\n", *readstate);
rcutorture_one_extend_check("after change", *readstate, statesnew, statesold, insoftirq);
}
/* Return the biggest extendables mask given current RCU and boot parameters. */
@ -2006,7 +2061,7 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
* critical section.
*/
static struct rt_read_seg *
rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
rcutorture_loop_extend(int *readstate, bool insoftirq, struct torture_random_state *trsp,
struct rt_read_seg *rtrsp)
{
int i;
@ -2021,7 +2076,7 @@ rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
for (j = 0; j < i; j++) {
mask = rcutorture_extend_mask(*readstate, trsp);
rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
rcutorture_one_extend(readstate, mask, insoftirq, trsp, &rtrsp[j]);
}
return &rtrsp[j];
}
@ -2051,7 +2106,7 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
WARN_ON_ONCE(!rcu_is_watching());
newstate = rcutorture_extend_mask(readstate, trsp);
rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
rcutorture_one_extend(&readstate, newstate, myid < 0, trsp, rtrsp++);
if (checkpolling) {
if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
cookie = cur_ops->get_gp_state();
@ -2064,13 +2119,13 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
!cur_ops->readlock_held || cur_ops->readlock_held());
if (p == NULL) {
/* Wait for rcu_torture_writer to get underway */
rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
rcutorture_one_extend(&readstate, 0, myid < 0, trsp, rtrsp);
return false;
}
if (p->rtort_mbtest == 0)
atomic_inc(&n_rcu_torture_mberror);
rcu_torture_reader_do_mbchk(myid, p, trsp);
rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
rtrsp = rcutorture_loop_extend(&readstate, myid < 0, trsp, rtrsp);
preempt_disable();
pipe_count = READ_ONCE(p->rtort_pipe_count);
if (pipe_count > RCU_TORTURE_PIPE_LEN) {
@ -2112,7 +2167,7 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
preempted = cur_ops->reader_blocked();
if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_CPU))
rt_last_cpu = raw_smp_processor_id();
rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
rcutorture_one_extend(&readstate, 0, myid < 0, trsp, rtrsp);
WARN_ON_ONCE(readstate);
// This next splat is expected behavior if leakpointer, especially
// for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.