Author: hselasky
Date: Fri Sep 28 10:28:22 2018
New Revision: 338993
URL: https://svnweb.freebsd.org/changeset/base/338993

Log:
  When multiple threads are involved receiving completion events in LibUSB
  make sure there is always a master polling thread, by setting the 
"ctx_handler"
  field in the context. Else the reception of completion events can stop.
  This happens if event threads are created and destroyed during runtime.
  
  Found by:             Ludovic Rousseau <[email protected]>
  PR:                   231742
  MFC after:            1 week
  Approved by:          re (kib)
  Sponsored by:         Mellanox Technologies

Modified:
  head/lib/libusb/libusb10_io.c

Modified: head/lib/libusb/libusb10_io.c
==============================================================================
--- head/lib/libusb/libusb10_io.c       Fri Sep 28 10:02:47 2018        
(r338992)
+++ head/lib/libusb/libusb10_io.c       Fri Sep 28 10:28:22 2018        
(r338993)
@@ -312,6 +312,9 @@ libusb_wait_for_event(libusb_context *ctx, struct time
        if (tv == NULL) {
                pthread_cond_wait(&ctx->ctx_cond,
                    &ctx->ctx_lock);
+               /* try to grab polling of actual events, if any */
+               if (ctx->ctx_handler == NO_THREAD)
+                       ctx->ctx_handler = pthread_self();
                return (0);
        }
        err = clock_gettime(CLOCK_MONOTONIC, &ts);
@@ -330,6 +333,9 @@ libusb_wait_for_event(libusb_context *ctx, struct time
        }
        err = pthread_cond_timedwait(&ctx->ctx_cond,
            &ctx->ctx_lock, &ts);
+       /* try to grab polling of actual events, if any */
+       if (ctx->ctx_handler == NO_THREAD)
+               ctx->ctx_handler = pthread_self();
 
        if (err == ETIMEDOUT)
                return (1);
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