From: Jeff Law <law@redhat.com>
To: "Carlos O'Donell" <carlos@systemhalted.org>
Cc: "Joseph S. Myers" <joseph@codesourcery.com>,
Mike Frysinger <vapier@gentoo.org>,
libc-alpha <libc-alpha@sourceware.org>,
libc-ports@sourceware.org,
Marcus Shawcroft <marcus.shawcroft@linaro.org>
Subject: Re: [PATCH] Memory fencing problem in pthread cancellation
Date: Thu, 31 Jan 2013 22:08:00 -0000 [thread overview]
Message-ID: <510AEB35.6090909@redhat.com> (raw)
In-Reply-To: <50F48DA4.4000407@systemhalted.org>
On 01/14/2013 03:58 PM, Carlos O'Donell wrote:
> You are correct, we need another entry for libgcc_s_resume, and we need
> to load that after the barrier, otherwise we won't call libgcc_s_resume.
>
> Something like this:
>
> diff --git a/ports/sysdeps/unix/sysv/linux/arm/nptl/unwind-forcedunwind.c b/ports/sysdeps/unix/sysv/linux/arm/nptl/unwind-forcedunwind.c
> index 58ca9ac..1e03b13 100644
> --- a/ports/sysdeps/unix/sysv/linux/arm/nptl/unwind-forcedunwind.c
> +++ b/ports/sysdeps/unix/sysv/linux/arm/nptl/unwind-forcedunwind.c
> @@ -104,7 +104,12 @@ asm (
> " mov r6, r0\n"
> " cmp r3, #0\n"
> " beq 4f\n"
> -"5: mov r0, r6\n"
> + atomic_asm_full_barrier()
> +"5: ldr r4, 6f\n"
> +" ldr r5, 7f\n"
> +"8: add r4, pc, r4\n"
> +" ldr r3, [r4, r5]\n"
> +" mov r0, r6\n"
> " ldmfd sp!, {r4, r5, r6, lr}\n"
> " " CFI_ADJUST_CFA_OFFSET (-16) "\n"
> " " CFI_RESTORE (r4) "\n"
> @@ -123,7 +128,13 @@ asm (
> #else
> "1: .word _GLOBAL_OFFSET_TABLE_ - 3b - 8\n"
> #endif
> -"2: .word libgcc_s_resume(GOTOFF)\n"
> +"2: .word libgcc_s_handle(GOTOFF)\n"
> +#ifdef __thumb2__
> +"6: .word _GLOBAL_OFFSET_TABLE_ - 8b - 4\n"
> +#else
> +"6: .word _GLOBAL_OFFSET_TABLE_ - 8b - 8\n"
> +#endif
> +"7: .word libgcc_s_resume(GOTOFF)\n"
> " .size _Unwind_Resume, .-_Unwind_Resume\n"
> );
Added. Likewise for the other changes. With one tweak:
[ ... ]
> @@ -76,7 +92,7 @@ asm (
> " " CFI_RESTORE (lr) "\n"
> " bx r3\n"
> " " CFI_RESTORE_STATE "\n"
> -"4: bl init\n"
> +"4: bl pthread_cancel_init\n"
> " ldr r3, [r4, r5]\n"
> " b 5b\n"
> " " CFI_ENDPROC "\n"
I got the impression via a later message from Joseph that this code was
supposed to call init rather than pthread_cancel_init. So I didn't
apply that hunk.
Updated patch with all the updates/fixes to be posted tomorrow AM.
Jeff
next prev parent reply other threads:[~2013-01-31 22:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <50F46969.1000305@redhat.com>
2013-01-14 22:11 ` Carlos O'Donell
2013-01-14 22:21 ` Joseph S. Myers
2013-01-14 22:58 ` Carlos O'Donell
2013-01-14 23:50 ` Joseph S. Myers
2013-01-31 22:08 ` Jeff Law [this message]
2013-01-31 22:05 ` Jeff Law
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