1. 14 Jul, 2023 2 commits
    • Waiman Long's avatar
      refscale: Fix uninitalized use of wait_queue_head_t · f5063e89
      Waiman Long authored
      Running the refscale test occasionally crashes the kernel with the
      following error:
      
      [ 8569.952896] BUG: unable to handle page fault for address: ffffffffffffffe8
      [ 8569.952900] #PF: supervisor read access in kernel mode
      [ 8569.952902] #PF: error_code(0x0000) - not-present page
      [ 8569.952904] PGD c4b048067 P4D c4b049067 PUD c4b04b067 PMD 0
      [ 8569.952910] Oops: 0000 [#1] PREEMPT_RT SMP NOPTI
      [ 8569.952916] Hardware name: Dell Inc. PowerEdge R750/0WMWCR, BIOS 1.2.4 05/28/2021
      [ 8569.952917] RIP: 0010:prepare_to_wait_event+0x101/0x190
        :
      [ 8569.952940] Call Trace:
      [ 8569.952941]  <TASK>
      [ 8569.952944]  ref_scale_reader+0x380/0x4a0 [refscale]
      [ 8569.952959]  kthread+0x10e/0x130
      [ 8569.952966]  ret_from_fork+0x1f/0x30
      [ 8569.952973]  </TASK>
      
      The likely cause is that init_waitqueue_head() is called after the call to
      the torture_create_kthread() function that creates the ref_scale_reader
      kthread.  Although this init_waitqueue_head() call will very likely
      complete before this kthread is created and starts running, it is
      possible that the calling kthread will be delayed between the calls to
      torture_create_kthread() and init_waitqueue_head().  In this case, the
      new kthread will use the waitqueue head before it is properly initialized,
      which is not good for the kernel's health and well-being.
      
      The above crash happened here:
      
      	static inline void __add_wait_queue(...)
      	{
      		:
      		if (!(wq->flags & WQ_FLAG_PRIORITY)) <=== Crash here
      
      The offset of flags from list_head entry in wait_queue_entry is
      -0x18. If reader_tasks[i].wq.head.next is NULL as allocated reader_task
      structure is zero initialized, the instruction will try to access address
      0xffffffffffffffe8, which is exactly the fault address listed above.
      
      This commit therefore invokes init_waitqueue_head() before creating
      the kthread.
      
      Fixes: 653ed64b ("refperf: Add a test to measure performance of read-side synchronization")
      Signed-off-by: default avatarWaiman Long <longman@redhat.com>
      Reviewed-by: default avatarQiuxu Zhuo <qiuxu.zhuo@intel.com>
      Reviewed-by: default avatarDavidlohr Bueso <dave@stgolabs.net>
      Acked-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
      Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      f5063e89
    • Paul E. McKenney's avatar
      refscale: Add CONFIG_PREEMPT_DYNAMIC=n to NOPREEMPT scenario · 8f78f046
      Paul E. McKenney authored
      It is no longer possible to build a kernel with a preemption-disabled
      RCU without use of CONFIG_PREEMPT_DYNAMIC=n.  This commit therefore
      adds CONFIG_PREEMPT_DYNAMIC=n to the refscale torture type's NOPREEMPT
      scenario file.
      Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      8f78f046
  2. 09 Jul, 2023 10 commits
  3. 08 Jul, 2023 28 commits