[incubator-nuttx] branch releases/10.0 updated: sched: Fix nx_waitid(), nx_waitpid(), nxtask_exithook() for SMP

[bt...@apache.org]

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btashton pushed a commit to branch releases/10.0
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git


The following commit(s) were added to refs/heads/releases/10.0 by this push:
     new ed25357  sched: Fix nx_waitid(), nx_waitpid(), nxtask_exithook() for SMP
ed25357 is described below

commit ed2535733ae9e35f5a9bbda50160af05859a252f
Author: Masayuki Ishikawa <ma...@gmail.com>
AuthorDate: Thu Nov 12 08:45:36 2020 +0900

    sched: Fix nx_waitid(), nx_waitpid(), nxtask_exithook() for SMP
    
    Summary:
    - I noticed waitpid_test stops with lc823450-xgevk:rndis
    - The condition was CONFIG_DEBUG_ASSERTION=y
    - Actually, the child task sent SIGCHILD but the parent couldn't catch the signal
    - Then, I found that nx_waitid(), nx_waitpid() use sched_lock()
    - However, a parent task and a child task are running on different CPUs
    - So, sched_lock() is not enough and need to use a critical section
    - Also, signal handling in nxtask_exithook() must be done in a critical section
    
    Impact:
    - SMP only
    
    Testing:
    - Tested with ostest with the following configurations
    - lc823450-xgevk:rndis (CONFIG_DEBUG_ASSERTION=y and n)
    - spresense:smp
    - spresense:wifi_smp (NCPUS=2 and 4)
    - sabre-6quad:smp (QEMU)
    - esp32-core:smp (QEMU)
    - maix-bit:smp (QEMU)
    - sim:smp
    
    Signed-off-by: Masayuki Ishikawa <Ma...@jp.sony.com>
---
 sched/sched/sched_waitid.c  | 13 +++++++++++++
 sched/sched/sched_waitpid.c | 34 ++++++++++++++++++++++++++++++----
 sched/task/task_exithook.c  | 12 +++++++++++-
 3 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/sched/sched/sched_waitid.c b/sched/sched/sched_waitid.c
index 2b8590d..86ee4b2 100644
--- a/sched/sched/sched_waitid.c
+++ b/sched/sched/sched_waitid.c
@@ -138,6 +138,14 @@ int nx_waitid(int idtype, id_t id, FAR siginfo_t *info, int options)
   sigemptyset(&set);
   nxsig_addset(&set, SIGCHLD);
 
+  /* NOTE: sched_lock() is not enough for SMP
+   * because the child task is running on another CPU
+   */
+
+#ifdef CONFIG_SMP
+  irqstate_t flags = enter_critical_section();
+#endif
+
   /* Disable pre-emption so that nothing changes while the loop executes */
 
   sched_lock();
@@ -374,6 +382,11 @@ int nx_waitid(int idtype, id_t id, FAR siginfo_t *info, int options)
 
 errout:
   sched_unlock();
+
+#ifdef CONFIG_SMP
+  leave_critical_section(flags);
+#endif
+
   return ret;
 }
 
diff --git a/sched/sched/sched_waitpid.c b/sched/sched/sched_waitpid.c
index c33186a..c4674ea 100644
--- a/sched/sched/sched_waitpid.c
+++ b/sched/sched/sched_waitpid.c
@@ -72,6 +72,14 @@ pid_t nx_waitpid(pid_t pid, int *stat_loc, int options)
 
   DEBUGASSERT(stat_loc);
 
+  /* NOTE: sched_lock() is not enough for SMP
+   * because the child task is running on another CPU
+   */
+
+#ifdef CONFIG_SMP
+  irqstate_t flags = enter_critical_section();
+#endif
+
   /* Disable pre-emption so that nothing changes in the following tests */
 
   sched_lock();
@@ -158,11 +166,15 @@ pid_t nx_waitpid(pid_t pid, int *stat_loc, int options)
 
   /* On success, return the PID */
 
-  sched_unlock();
-  return pid;
+  ret = pid;
 
 errout:
   sched_unlock();
+
+#ifdef CONFIG_SMP
+  leave_critical_section(flags);
+#endif
+
   return ret;
 }
 
@@ -199,6 +211,14 @@ pid_t nx_waitpid(pid_t pid, int *stat_loc, int options)
   sigemptyset(&set);
   nxsig_addset(&set, SIGCHLD);
 
+  /* NOTE: sched_lock() is not enough for SMP
+   * because the child task is running on another CPU
+   */
+
+#ifdef CONFIG_SMP
+  irqstate_t flags = enter_critical_section();
+#endif
+
   /* Disable pre-emption so that nothing changes while the loop executes */
 
   sched_lock();
@@ -438,11 +458,17 @@ pid_t nx_waitpid(pid_t pid, int *stat_loc, int options)
         }
     }
 
-  sched_unlock();
-  return pid;
+  /* On success, return the PID */
+
+  ret = pid;
 
 errout:
   sched_unlock();
+
+#ifdef CONFIG_SMP
+  leave_critical_section(flags);
+#endif
+
   return ret;
 }
 #endif /* CONFIG_SCHED_HAVE_PARENT */
diff --git a/sched/task/task_exithook.c b/sched/task/task_exithook.c
index 335638e..48cb5c8 100644
--- a/sched/task/task_exithook.c
+++ b/sched/task/task_exithook.c
@@ -639,7 +639,13 @@ void nxtask_exithook(FAR struct tcb_s *tcb, int status, bool nonblocking)
 
   nxtask_recover(tcb);
 
-  /* Send the SIGCHILD signal to the parent task group */
+  /* NOTE: signal handling needs to be done in a criticl section */
+
+#ifdef CONFIG_SMP
+  irqstate_t flags = enter_critical_section();
+#endif
+
+  /* Send the SIGCHLD signal to the parent task group */
 
   nxtask_signalparent(tcb, status);
 
@@ -673,6 +679,10 @@ void nxtask_exithook(FAR struct tcb_s *tcb, int status, bool nonblocking)
 
   nxsig_cleanup(tcb); /* Deallocate Signal lists */
 
+#ifdef CONFIG_SMP
+  leave_critical_section(flags);
+#endif
+
   /* This function can be re-entered in certain cases.  Set a flag
    * bit in the TCB to not that we have already completed this exit
    * processing.