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Viewing changes to snap/patches/use-sdl-semaphores.patch

  • Committer: Olivier Tilloy
  • Date: 2021-08-16 13:43:20 UTC
  • Revision ID: olivier@tilloy.net-20210816134320-e1z4qlhz8ix3wzge
https://launchpad.net/bugs/1756885
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snap/patches/use-sdl-semaphores.patch
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Description: Use SDL semaphores instead of named semaphores, that fail under strict confinement
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Forwarded: no
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Author: Olivier Tilloy <olivier@tilloy.net>
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Last-Update: 2017-05-15
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--- a/source/tools/atlas/GameInterface/MessagePasserImpl.h
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+++ b/source/tools/atlas/GameInterface/MessagePasserImpl.h
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@@ -20,6 +20,7 @@
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 #include "MessagePasser.h"
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+#include "lib/external_libraries/libsdl.h"
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 #include "ps/ThreadUtil.h"
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 #include "ps/CStr.h"
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 #include <queue>
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@@ -40,8 +41,7 @@ public:
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 private:
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        CMutex m_Mutex;
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-       CStr m_SemaphoreName;
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-       sem_t* m_Semaphore;
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+       SDL_sem* m_Semaphore;
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        std::queue<AtlasMessage::IMessage*> m_Queue;
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        bool m_Trace;
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 };
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--- a/source/tools/atlas/GameInterface/MessagePasserImpl.cpp
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+++ b/source/tools/atlas/GameInterface/MessagePasserImpl.cpp
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@@ -32,39 +32,10 @@ using namespace AtlasMessage;
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 MessagePasserImpl::MessagePasserImpl()
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 : m_Trace(false), m_Semaphore(NULL)
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 {
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-       int tries = 0;
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-       while (tries++ < 16) // some arbitrary cut-off point to avoid infinite loops
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-       {
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-               static char name[64];
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-               sprintf_s(name, ARRAY_SIZE(name), "/wfg-atlas-msgpass-%d-%d",
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-                               (int)rand(1, 1000), (int)(time(0)%1000));
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-               sem_t* sem = sem_open(name, O_CREAT | O_EXCL, 0700, 0);
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-
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-               // This cast should not be necessary, but apparently SEM_FAILED is not
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-               // a value of a pointer type
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-               if (sem == (sem_t*)SEM_FAILED || !sem)
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-               {
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-                       int err = errno;
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-                       if (err == EEXIST)
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-                       {
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-                               // Semaphore already exists - try another one
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-                               continue;
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-                       }
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-                       // Otherwise, it's a probably-fatal error
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-                       debug_warn(L"sem_open failed");
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-                       break;
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-               }
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-               // Succeeded - use this semaphore
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-               m_Semaphore = sem;
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-               m_SemaphoreName = name;
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-               break;
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-       }
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-
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-       if (! m_Semaphore)
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+       m_Semaphore = SDL_CreateSemaphore(0);
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+       if (m_Semaphore == NULL)
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        {
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                debug_warn(L"Failed to create semaphore for Atlas - giving up");
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-               // We will probably crash later - maybe we could fall back on sem_init, if this
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-               // ever fails in practice
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        }
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 }
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@@ -72,9 +43,7 @@ MessagePasserImpl::~MessagePasserImpl()
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 {
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        if (m_Semaphore)
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        {
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-               // Clean up
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-               sem_close(m_Semaphore);
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-               sem_unlink(m_SemaphoreName.c_str());
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+               SDL_DestroySemaphore(m_Semaphore);
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        }
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 }
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@@ -165,19 +134,7 @@ void MessagePasserImpl::Query(QueryMessa
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 //     while (0 != (err = sem_timedwait(psem, &abs_timeout)))
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 // #endif
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-       while (0 != sem_wait(m_Semaphore))
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-       {
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-               // If timed out, call callback and try again
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-//             if (errno == ETIMEDOUT)
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-//                     timeoutCallback();
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-//             else
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-               // Keep retrying while EINTR, but other errors are probably fatal
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-               if (errno != EINTR)
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-               {
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-                       debug_warn(L"Semaphore wait failed");
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-                       return; // (leaks the semaphore)
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-               }
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-       }
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+       SDL_SemWait(m_Semaphore);
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        // Clean up
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        qry->m_Semaphore = NULL;
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--- a/source/tools/atlas/GameInterface/GameLoop.cpp
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+++ b/source/tools/atlas/GameInterface/GameLoop.cpp
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@@ -184,7 +184,7 @@ static void* RunEngine(void* data)
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                                {
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                                        // For queries, we need to notify MessagePasserImpl::Query
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                                        // that the query has now been processed.
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-                                       sem_post((sem_t*) static_cast<QueryMessage*>(msg)->m_Semaphore);
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+                                       SDL_SemPost((SDL_sem*) static_cast<QueryMessage*>(msg)->m_Semaphore);
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                                        // (msg may have been destructed at this point, so don't use it again)
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                                        // It's quite possible that the querier is going to do a tiny