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context: Ensure mainloop is idle before enumeration completes

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This ensures that we have processed all hotplug events before
considering enumeration to be complete. This is important due to USB
persist being turned off. At resume time, devices will disappear and
immediately re-appear. In this situatoin, enumerate could first see the
old state with a removed device resulting in it to not be discovered.

As a hotplug event is semingly emitted by the kernel immediately, we
can simply make sure to process this hotplug event before returning
from enumerate.

Closes: fprintd#119
This commit is contained in:
Benjamin Berg
2021-11-24 12:09:18 +01:00
committed by Benjamin Berg
parent a033154b2e
commit 05fd2c58cb
1 changed files with 14 additions and 2 deletions
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16
libfprint/fp-context.c
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@@ -426,6 +426,7 @@ void
fp_context_enumerate (FpContext *context) fp_context_enumerate (FpContext *context)
{ {
FpContextPrivate *priv = fp_context_get_instance_private (context); FpContextPrivate *priv = fp_context_get_instance_private (context);
gboolean dispatched;
gint i; gint i;
g_return_if_fail (FP_IS_CONTEXT (context)); g_return_if_fail (FP_IS_CONTEXT (context));
@@ -564,8 +565,19 @@ fp_context_enumerate (FpContext *context)
} }
#endif #endif
while (priv->pending_devices) /* Iterate until 1. we have no pending devices, and 2. the mainloop is idle
g_main_context_iteration (NULL, TRUE); * This takes care of processing hotplug events that happened during
* enumeration.
* This is important due to USB `persist` being turned off. At resume time,
* devices will disappear and immediately re-appear. In this situation,
* enumerate could first see the old state with a removed device resulting
* in it to not be discovered.
* As a hotplug event is seemingly emitted by the kernel immediately, we can
* simply make sure to process all events before returning from enumerate.
*/
dispatched = TRUE;
while (priv->pending_devices || dispatched)
dispatched = g_main_context_iteration (NULL, !!priv->pending_devices);
} }
/** /**