Fix T38873: Crashing on undo of ocean modifier.

Issue of this bug is that most part of fftw is not thread safe, only compute-intensive fftw_execute & co are.

Since smoke was affected by this issue as well, a global fftw mutex was added to BLI_threads.
Audaspace also uses fftw in one of its readers (AUD_BandPassReader.cpp),
but this is not an issue currently since this code is disabled in CMake/scons files.

There was another threading issue with smoke, we need to copy dm used by emit_from_derivedmesh(),
as it is modified by this func.

Reviewers: sergey, brecht

Reviewed By: brecht

CC: brecht

Differential Revision: https://developer.blender.org/D374

source/blender/blenkernel/intern/ocean.c

@@ -846,6 +846,8 @@ void BKE_init_ocean(struct Ocean *o, int M, int N, float Lx, float Lz, float V,
 	o->_fft_in = (fftw_complex *)MEM_mallocN(o->_M * (1 + o->_N / 2) * sizeof(fftw_complex), "ocean_fft_in");
 	o->_htilda = (fftw_complex *)MEM_mallocN(o->_M * (1 + o->_N / 2) * sizeof(fftw_complex), "ocean_htilda");
 
+	BLI_lock_thread(LOCK_FFTW);
+
 	if (o->_do_disp_y) {
 		o->_disp_y = (double *)MEM_mallocN(o->_M * o->_N * sizeof(double), "ocean_disp_y");
 		o->_disp_y_plan = fftw_plan_dft_c2r_2d(o->_M, o->_N, o->_fft_in, o->_disp_y, FFTW_ESTIMATE);
@@ -890,6 +892,8 @@ void BKE_init_ocean(struct Ocean *o, int M, int N, float Lx, float Lz, float V,
 		o->_Jxz_plan = fftw_plan_dft_c2r_2d(o->_M, o->_N, o->_fft_in_jxz, o->_Jxz, FFTW_ESTIMATE);
 	}
 
+	BLI_unlock_thread(LOCK_FFTW);
+
 	BLI_rw_mutex_unlock(&o->oceanmutex);
 
 	set_height_normalize_factor(o);
@@ -903,6 +907,8 @@ void BKE_free_ocean_data(struct Ocean *oc)
 
 	BLI_rw_mutex_lock(&oc->oceanmutex, THREAD_LOCK_WRITE);
 
+	BLI_lock_thread(LOCK_FFTW);
+
 	if (oc->_do_disp_y) {
 		fftw_destroy_plan(oc->_disp_y_plan);
 		MEM_freeN(oc->_disp_y);
@@ -939,6 +945,8 @@ void BKE_free_ocean_data(struct Ocean *oc)
 		MEM_freeN(oc->_Jxz);
 	}
 
+	BLI_unlock_thread(LOCK_FFTW);
+
 	if (oc->_fft_in)
 		MEM_freeN(oc->_fft_in);
 

source/blender/blenkernel/intern/smoke.c

@@ -207,7 +207,14 @@ void smoke_reallocate_highres_fluid(SmokeDomainSettings *sds, float dx, int res[
 		sds->wt = NULL;
 		return;
 	}
+
+	/* smoke_turbulence_init uses non-threadsafe functions from fftw3 lib (like fftw_plan & co). */
+	BLI_lock_thread(LOCK_FFTW);
+
 	sds->wt = smoke_turbulence_init(res, sds->amplify + 1, sds->noise, BLI_temporary_dir(), use_fire, use_colors);
+
+	BLI_unlock_thread(LOCK_FFTW);
+
 	sds->res_wt[0] = res[0] * (sds->amplify + 1);
 	sds->res_wt[1] = res[1] * (sds->amplify + 1);
 	sds->res_wt[2] = res[2] * (sds->amplify + 1);
@@ -1550,7 +1557,7 @@ static void emit_from_derivedmesh(Object *flow_ob, SmokeDomainSettings *sds, Smo
 {
 	if (!sfs->dm) return;
 	{
-		DerivedMesh *dm = sfs->dm;
+		DerivedMesh *dm;
 		int defgrp_index = sfs->vgroup_density - 1;
 		MDeformVert *dvert = NULL;
 		MVert *mvert = NULL;
@@ -1566,6 +1573,11 @@ static void emit_from_derivedmesh(Object *flow_ob, SmokeDomainSettings *sds, Smo
 		int min[3], max[3], res[3];
 		int hires_multiplier = 1;
 
+		/* copy derivedmesh for thread safety because we modify it,
+		 * main issue is its VertArray being modified, then replaced and freed
+		 */
+		dm = CDDM_copy(sfs->dm);
+
 		CDDM_calc_normals(dm);
 		mvert = dm->getVertArray(dm);
 		mvert_orig = dm->dupVertArray(dm);  /* copy original mvert and restore when done */

source/blender/blenlib/BLI_threads.h

@@ -88,6 +88,7 @@ int     BLI_system_num_threads_override_get(void);
 #define LOCK_NODES      6
 #define LOCK_MOVIECLIP  7
 #define LOCK_COLORMANAGE 8
+#define LOCK_FFTW       9
 
 void    BLI_lock_thread(int type);
 void    BLI_unlock_thread(int type);

source/blender/blenlib/intern/threads.c

@@ -121,6 +121,7 @@ static pthread_mutex_t _opengl_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t _nodes_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t _movieclip_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t _colormanage_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t _fftw_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_t mainid;
 static int thread_levels = 0;  /* threads can be invoked inside threads */
 static int num_threads_override = 0;
@@ -399,6 +400,8 @@ void BLI_lock_thread(int type)
 		pthread_mutex_lock(&_movieclip_lock);
 	else if (type == LOCK_COLORMANAGE)
 		pthread_mutex_lock(&_colormanage_lock);
+	else if (type == LOCK_FFTW)
+		pthread_mutex_lock(&_fftw_lock);
 }
 
 void BLI_unlock_thread(int type)
@@ -421,6 +424,8 @@ void BLI_unlock_thread(int type)
 		pthread_mutex_unlock(&_movieclip_lock);
 	else if (type == LOCK_COLORMANAGE)
 		pthread_mutex_unlock(&_colormanage_lock);
+	else if (type == LOCK_FFTW)
+		pthread_mutex_unlock(&_fftw_lock);
 }
 
 /* Mutex Locks */