From: John David Anglin dave.anglin@bell.net
commit be6577af0cef934ccb036445314072e8cb9217b9 upstream.
Stalls are quite frequent with recent kernels. I enabled CONFIG_SOFTLOCKUP_DETECTOR and I caught the following stall:
watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [cc1:22803] CPU: 0 PID: 22803 Comm: cc1 Not tainted 5.6.17+ #3 Hardware name: 9000/800/rp3440 IAOQ[0]: d_alloc_parallel+0x384/0x688 IAOQ[1]: d_alloc_parallel+0x388/0x688 RP(r2): d_alloc_parallel+0x134/0x688 Backtrace: [<000000004036974c>] __lookup_slow+0xa4/0x200 [<0000000040369fc8>] walk_component+0x288/0x458 [<000000004036a9a0>] path_lookupat+0x88/0x198 [<000000004036e748>] filename_lookup+0xa0/0x168 [<000000004036e95c>] user_path_at_empty+0x64/0x80 [<000000004035d93c>] vfs_statx+0x104/0x158 [<000000004035dfcc>] __do_sys_lstat64+0x44/0x80 [<000000004035e5a0>] sys_lstat64+0x20/0x38 [<0000000040180054>] syscall_exit+0x0/0x14
The code was stuck in this loop in d_alloc_parallel:
4037d414: 0e 00 10 dc ldd 0(r16),ret0 4037d418: c7 fc 5f ed bb,< ret0,1f,4037d414 <d_alloc_parallel+0x384> 4037d41c: 08 00 02 40 nop
This is the inner loop of bit_spin_lock which is called by hlist_bl_unlock in d_alloc_parallel:
static inline void bit_spin_lock(int bitnum, unsigned long *addr) { /* * Assuming the lock is uncontended, this never enters * the body of the outer loop. If it is contended, then * within the inner loop a non-atomic test is used to * busywait with less bus contention for a good time to * attempt to acquire the lock bit. */ preempt_disable(); #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) while (unlikely(test_and_set_bit_lock(bitnum, addr))) { preempt_enable(); do { cpu_relax(); } while (test_bit(bitnum, addr)); preempt_disable(); } #endif __acquire(bitlock); }
After consideration, I realized that we must be losing bit unlocks. Then, I noticed that we missed defining atomic64_set_release(). Adding this define fixes the stalls in bit operations.
Signed-off-by: Dave Anglin dave.anglin@bell.net Cc: stable@vger.kernel.org Signed-off-by: Helge Deller deller@gmx.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/parisc/include/asm/atomic.h | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/parisc/include/asm/atomic.h +++ b/arch/parisc/include/asm/atomic.h @@ -255,6 +255,8 @@ atomic64_set(atomic64_t *v, s64 i) _atomic_spin_unlock_irqrestore(v, flags); }
+#define atomic64_set_release(v, i) atomic64_set((v), (i)) + static __inline__ s64 atomic64_read(const atomic64_t *v) {