svn commit: r362119 - in head/sys: amd64/amd64 i386/i386

[Eric van Gyzen]

Author: vangyzen
Date: Fri Jun 12 21:10:45 2020
New Revision: 362119
URL: https://svnweb.freebsd.org/changeset/base/362119

Log:
  FPU init: Do potentially blocking operations before disabling interrupts
  
  In particular, uma_zcreate creates sysctl oids, which locks an sx lock,
  which uses IPIs under contention.  IPIs tend not to work very well
  when interrupts are disabled.  Who knew, right?
  
  Reviewed by:	cem kib
  MFC after:	2 weeks
  Sponsored by:	Dell EMC Isilon
  Differential Revision:	https://reviews.freebsd.org/D25098

Modified:
  head/sys/amd64/amd64/fpu.c
  head/sys/i386/i386/npx.c

Modified: head/sys/amd64/amd64/fpu.c
==============================================================================
--- head/sys/amd64/amd64/fpu.c	Fri Jun 12 20:39:42 2020	(r362118)
+++ head/sys/amd64/amd64/fpu.c	Fri Jun 12 21:10:45 2020	(r362119)
@@ -368,8 +368,18 @@ fpuinitstate(void *arg __unused)
 	register_t saveintr;
 	int cp[4], i, max_ext_n;
 
+	/* Do potentially blocking operations before disabling interrupts. */
+	fpu_save_area_zone = uma_zcreate("FPU_save_area",
+	    cpu_max_ext_state_size, NULL, NULL, NULL, NULL,
+	    XSAVE_AREA_ALIGN - 1, 0);
 	fpu_initialstate = malloc(cpu_max_ext_state_size, M_DEVBUF,
 	    M_WAITOK | M_ZERO);
+	if (use_xsave) {
+		max_ext_n = flsl(xsave_mask);
+		xsave_area_desc = malloc(max_ext_n * sizeof(struct
+		    xsave_area_elm_descr), M_DEVBUF, M_WAITOK | M_ZERO);
+	}
+
 	saveintr = intr_disable();
 	stop_emulating();
 
@@ -399,9 +409,6 @@ fpuinitstate(void *arg __unused)
 		    offsetof(struct xstate_hdr, xstate_bv));
 		*xstate_bv = XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
 
-		max_ext_n = flsl(xsave_mask);
-		xsave_area_desc = malloc(max_ext_n * sizeof(struct
-		    xsave_area_elm_descr), M_DEVBUF, M_WAITOK | M_ZERO);
 		/* x87 state */
 		xsave_area_desc[0].offset = 0;
 		xsave_area_desc[0].size = 160;
@@ -415,10 +422,6 @@ fpuinitstate(void *arg __unused)
 			xsave_area_desc[i].size = cp[0];
 		}
 	}
-
-	fpu_save_area_zone = uma_zcreate("FPU_save_area",
-	    cpu_max_ext_state_size, NULL, NULL, NULL, NULL,
-	    XSAVE_AREA_ALIGN - 1, 0);
 
 	start_emulating();
 	intr_restore(saveintr);

Modified: head/sys/i386/i386/npx.c
==============================================================================
--- head/sys/i386/i386/npx.c	Fri Jun 12 20:39:42 2020	(r362118)
+++ head/sys/i386/i386/npx.c	Fri Jun 12 21:10:45 2020	(r362119)
@@ -479,8 +479,21 @@ npxinitstate(void *arg __unused)
 	if (!hw_float)
 		return;
 
+	/* Do potentially blocking operations before disabling interrupts. */
+	fpu_save_area_zone = uma_zcreate("FPU_save_area",
+	    cpu_max_ext_state_size, NULL, NULL, NULL, NULL,
+	    XSAVE_AREA_ALIGN - 1, 0);
 	npx_initialstate = malloc(cpu_max_ext_state_size, M_DEVBUF,
 	    M_WAITOK | M_ZERO);
+	if (use_xsave) {
+		if (xsave_mask >> 32 != 0)
+			max_ext_n = fls(xsave_mask >> 32) + 32;
+		else
+			max_ext_n = fls(xsave_mask);
+		xsave_area_desc = malloc(max_ext_n * sizeof(struct
+		    xsave_area_elm_descr), M_DEVBUF, M_WAITOK | M_ZERO);
+	}
+
 	saveintr = intr_disable();
 	stop_emulating();
 
@@ -522,12 +535,6 @@ npxinitstate(void *arg __unused)
 		    offsetof(struct xstate_hdr, xstate_bv));
 		*xstate_bv = XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
 
-		if (xsave_mask >> 32 != 0)
-			max_ext_n = fls(xsave_mask >> 32) + 32;
-		else
-			max_ext_n = fls(xsave_mask);
-		xsave_area_desc = malloc(max_ext_n * sizeof(struct
-		    xsave_area_elm_descr), M_DEVBUF, M_WAITOK | M_ZERO);
 		/* x87 state */
 		xsave_area_desc[0].offset = 0;
 		xsave_area_desc[0].size = 160;
@@ -541,10 +548,6 @@ npxinitstate(void *arg __unused)
 			xsave_area_desc[i].size = cp[0];
 		}
 	}
-
-	fpu_save_area_zone = uma_zcreate("FPU_save_area",
-	    cpu_max_ext_state_size, NULL, NULL, NULL, NULL,
-	    XSAVE_AREA_ALIGN - 1, 0);
 
 	start_emulating();
 	intr_restore(saveintr);