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srcu: Avoid NULL dereference in srcu_torture_stats_print()

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You really shouldn't invoke srcu_torture_stats_print() after invoking
cleanup_srcu_struct(), but there is really no reason to get a
compiler-obfuscated per-CPU-variable NULL pointer dereference as the
diagnostic.  This commit therefore checks for NULL ->sda and makes a
more polite console-message complaint in that case.

Co-developed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-01-27 11:43:11 -08:00
parent db8f1471c6
commit 4a230f8046
1 changed files with 31 additions and 25 deletions
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56
kernel/rcu/srcutree.c
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@ -1477,37 +1477,43 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
idx = ssp->srcu_idx & 0x1;
if (ss_state < 0 || ss_state >= ARRAY_SIZE(srcu_size_state_name))
ss_state_idx = ARRAY_SIZE(srcu_size_state_name) - 1;
pr_alert("%s%s Tree SRCU g%ld state %d (%s) per-CPU(idx=%d):",
pr_alert("%s%s Tree SRCU g%ld state %d (%s)",
tt, tf, rcu_seq_current(&ssp->srcu_gp_seq), ss_state,
srcu_size_state_name[ss_state_idx], idx);
for_each_possible_cpu(cpu) {
unsigned long l0, l1;
unsigned long u0, u1;
long c0, c1;
struct srcu_data *sdp;
srcu_size_state_name[ss_state_idx]);
if (!ssp->sda) {
// Called after cleanup_srcu_struct(), perhaps.
pr_cont(" No per-CPU srcu_data structures (->sda == NULL).\n");
} else {
pr_cont(" per-CPU(idx=%d):", idx);
for_each_possible_cpu(cpu) {
unsigned long l0, l1;
unsigned long u0, u1;
long c0, c1;
struct srcu_data *sdp;
sdp = per_cpu_ptr(ssp->sda, cpu);
u0 = data_race(sdp->srcu_unlock_count[!idx]);
u1 = data_race(sdp->srcu_unlock_count[idx]);
sdp = per_cpu_ptr(ssp->sda, cpu);
u0 = data_race(sdp->srcu_unlock_count[!idx]);
u1 = data_race(sdp->srcu_unlock_count[idx]);
/*
* Make sure that a lock is always counted if the corresponding
* unlock is counted.
*/
smp_rmb();
/*
* Make sure that a lock is always counted if the corresponding
* unlock is counted.
*/
smp_rmb();
l0 = data_race(sdp->srcu_lock_count[!idx]);
l1 = data_race(sdp->srcu_lock_count[idx]);
l0 = data_race(sdp->srcu_lock_count[!idx]);
l1 = data_race(sdp->srcu_lock_count[idx]);
c0 = l0 - u0;
c1 = l1 - u1;
pr_cont(" %d(%ld,%ld %c)",
cpu, c0, c1,
"C."[rcu_segcblist_empty(&sdp->srcu_cblist)]);
s0 += c0;
s1 += c1;
c0 = l0 - u0;
c1 = l1 - u1;
pr_cont(" %d(%ld,%ld %c)",
cpu, c0, c1,
"C."[rcu_segcblist_empty(&sdp->srcu_cblist)]);
s0 += c0;
s1 += c1;
}
pr_cont(" T(%ld,%ld)\n", s0, s1);
}
pr_cont(" T(%ld,%ld)\n", s0, s1);
if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 2)
WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_ALLOC);
}