Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 1ca7d67c authored by John Stultz's avatar John Stultz Committed by Ingo Molnar
Browse files

seqcount: Add lockdep functionality to seqcount/seqlock structures 



Currently seqlocks and seqcounts don't support lockdep.

After running across a seqcount related deadlock in the timekeeping
code, I used a less-refined and more focused variant of this patch
to narrow down the cause of the issue.

This is a first-pass attempt to properly enable lockdep functionality
on seqlocks and seqcounts.

Since seqcounts are used in the vdso gettimeofday code, I've provided
non-lockdep accessors for those needs.

I've also handled one case where there were nested seqlock writers
and there may be more edge cases.

Comments and feedback would be appreciated!

Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/1381186321-4906-3-git-send-email-john.stultz@linaro.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 827da44c

arch/x86/vdso/vclock_gettime.c

+4 −4
Original line number Diff line number Diff line
@@ -178,7 +178,7 @@ notrace static int __always_inline do_realtime(struct timespec *ts) 


	ts->tv_nsec = 0;

	do {

		seq = read_seqcount_begin(&gtod->seq);

		seq = read_seqcount_begin_no_lockdep(&gtod->seq);

		mode = gtod->clock.vclock_mode;

		ts->tv_sec = gtod->wall_time_sec;

		ns = gtod->wall_time_snsec;
@@ -198,7 +198,7 @@ notrace static int do_monotonic(struct timespec *ts) 


	ts->tv_nsec = 0;

	do {

		seq = read_seqcount_begin(&gtod->seq);

		seq = read_seqcount_begin_no_lockdep(&gtod->seq);

		mode = gtod->clock.vclock_mode;

		ts->tv_sec = gtod->monotonic_time_sec;

		ns = gtod->monotonic_time_snsec;
@@ -214,7 +214,7 @@ notrace static int do_realtime_coarse(struct timespec *ts) 
{

	unsigned long seq;

	do {

		seq = read_seqcount_begin(&gtod->seq);

		seq = read_seqcount_begin_no_lockdep(&gtod->seq);

		ts->tv_sec = gtod->wall_time_coarse.tv_sec;

		ts->tv_nsec = gtod->wall_time_coarse.tv_nsec;

	} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
@@ -225,7 +225,7 @@ notrace static int do_monotonic_coarse(struct timespec *ts) 
{

	unsigned long seq;

	do {

		seq = read_seqcount_begin(&gtod->seq);

		seq = read_seqcount_begin_no_lockdep(&gtod->seq);

		ts->tv_sec = gtod->monotonic_time_coarse.tv_sec;

		ts->tv_nsec = gtod->monotonic_time_coarse.tv_nsec;

	} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));

fs/dcache.c

+2 −2
Original line number Diff line number Diff line
@@ -2574,7 +2574,7 @@ static void __d_move(struct dentry * dentry, struct dentry * target) 
	dentry_lock_for_move(dentry, target);



	write_seqcount_begin(&dentry->d_seq);

	write_seqcount_begin(&target->d_seq);

	write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);



	/* __d_drop does write_seqcount_barrier, but they're OK to nest. */
@@ -2706,7 +2706,7 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) 
	dentry_lock_for_move(anon, dentry);



	write_seqcount_begin(&dentry->d_seq);

	write_seqcount_begin(&anon->d_seq);

	write_seqcount_begin_nested(&anon->d_seq, DENTRY_D_LOCK_NESTED);



	dparent = dentry->d_parent;

fs/fs_struct.c

+1 −1
Original line number Diff line number Diff line
@@ -161,6 +161,6 @@ EXPORT_SYMBOL(current_umask); 
struct fs_struct init_fs = {

	.users		= 1,

	.lock		= __SPIN_LOCK_UNLOCKED(init_fs.lock),

	.seq		= SEQCNT_ZERO,

	.seq		= SEQCNT_ZERO(init_fs.seq),

	.umask		= 0022,

};

include/linux/init_task.h

+4 −4
Original line number Diff line number Diff line
@@ -32,10 +32,10 @@ extern struct fs_struct init_fs; 
#endif



#ifdef CONFIG_CPUSETS

#define INIT_CPUSET_SEQ							\

	.mems_allowed_seq = SEQCNT_ZERO,

#define INIT_CPUSET_SEQ(tsk)							\

	.mems_allowed_seq = SEQCNT_ZERO(tsk.mems_allowed_seq),

#else

#define INIT_CPUSET_SEQ

#define INIT_CPUSET_SEQ(tsk)

#endif



#define INIT_SIGNALS(sig) {						\
@@ -220,7 +220,7 @@ extern struct task_group root_task_group; 
	INIT_FTRACE_GRAPH						\

	INIT_TRACE_RECURSION						\

	INIT_TASK_RCU_PREEMPT(tsk)					\

	INIT_CPUSET_SEQ							\

	INIT_CPUSET_SEQ(tsk)						\

	INIT_VTIME(tsk)							\

}

include/linux/lockdep.h

+6 −2
Original line number Diff line number Diff line
@@ -497,6 +497,10 @@ static inline void print_irqtrace_events(struct task_struct *curr) 
#define rwlock_acquire_read(l, s, t, i)		lock_acquire_shared_recursive(l, s, t, NULL, i)

#define rwlock_release(l, n, i)			lock_release(l, n, i)



#define seqcount_acquire(l, s, t, i)		lock_acquire_exclusive(l, s, t, NULL, i)

#define seqcount_acquire_read(l, s, t, i)	lock_acquire_shared_recursive(l, s, t, NULL, i)

#define seqcount_release(l, n, i)		lock_release(l, n, i)



#define mutex_acquire(l, s, t, i)		lock_acquire_exclusive(l, s, t, NULL, i)

#define mutex_acquire_nest(l, s, t, n, i)	lock_acquire_exclusive(l, s, t, n, i)

#define mutex_release(l, n, i)			lock_release(l, n, i)