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Commit db1231dc authored Dec 09, 2015 by Anton Blanchard Committed by Michael Ellerman Dec 10, 2015

powerpc: Fix DSCR inheritance over fork()



Two DSCR tests have a hack in them:

	/*
	 * XXX: Force a context switch out so that DSCR
	 * current value is copied into the thread struct
	 * which is required for the child to inherit the
	 * changed value.
	 */
	sleep(1);

We should not be working around this in the testcase, it is a kernel bug.
Fix it by copying the current DSCR to the child, instead of what we
had in the thread struct at last context switch.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent 20dbe670

arch/powerpc/kernel/process.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1287,7 +1287,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
		#ifdef CONFIG_PPC64
		if (cpu_has_feature(CPU_FTR_DSCR)) {
		p->thread.dscr_inherit = current->thread.dscr_inherit;
		p->thread.dscr = current->thread.dscr;
		p->thread.dscr = mfspr(SPRN_DSCR);
		}
		if (cpu_has_feature(CPU_FTR_HAS_PPR))
		p->thread.ppr = INIT_PPR;

tools/testing/selftests/powerpc/dscr/dscr_inherit_exec_test.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -60,14 +60,6 @@ int dscr_inherit_exec(void)
		else
		set_dscr(dscr);

		/*
		* XXX: Force a context switch out so that DSCR
		* current value is copied into the thread struct
		* which is required for the child to inherit the
		* changed value.
		*/
		sleep(1);

		pid = fork();
		if (pid == -1) {
		perror("fork() failed");

tools/testing/selftests/powerpc/dscr/dscr_inherit_test.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -40,14 +40,6 @@ int dscr_inherit(void)
		else
		set_dscr(dscr);

		/*
		* XXX: Force a context switch out so that DSCR
		* current value is copied into the thread struct
		* which is required for the child to inherit the
		* changed value.
		*/
		sleep(1);

		pid = fork();
		if (pid == -1) {
		perror("fork() failed");