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arch/x86_64/intel64: fix signal delivery race in x86_64_sigdeliver

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copy logic from arm64 to fix SMP bugs in the signal trampoline
caused signals to be lost or mis-delivered in ostest signest_test
on qemu-intel64/jumbo.

Also update comments so this logic is easier to follow

Signed-off-by: raiden00pl <raiden00@railab.me>
This commit is contained in:
raiden00pl
2026-04-20 20:07:07 +02:00
committed by Xiang Xiao
parent e79cade0e3
commit a9e9607d95
1 changed files with 35 additions and 17 deletions
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arch/x86_64/src/intel64/intel64_sigdeliver.c
+35 -17
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@@ -86,10 +86,10 @@ void x86_64_sigdeliver(void)
x86_64_copystate(regs, rtcb->xcp.regs);
retry:
#ifdef CONFIG_SMP
/* In the SMP case, up_schedule_sigaction(0) will have incremented
* 'irqcount' in order to force us into a critical section. Save the
* pre-incremented irqcount.
/* Save the pre-incremented irqcount so we can restore it before resuming
* the interrupted thread.
*/
saved_irqcount = rtcb->irqcount;
@@ -125,11 +125,39 @@ void x86_64_sigdeliver(void)
sinfo("Resuming\n");
#ifdef CONFIG_SMP
enter_critical_section();
#else
/* Restore the saved 'irqcount' plus one extra to enforce the critical
* section while we check for any newly queued signal actions and modify
* the saved regs. The extra is dropped below with a final
* leave_critical_section(), yielding net irqcount == saved_irqcount.
*/
DEBUGASSERT(rtcb->irqcount == 0);
while (rtcb->irqcount < saved_irqcount + 1)
{
enter_critical_section();
}
#endif
#ifndef CONFIG_SUPPRESS_INTERRUPTS
up_irq_save();
#endif
/* A new signal action may have been queued while we were returning from
* nxsig_deliver() (after its empty-queue check but before we re-entered
* the critical section). If so, re-run the delivery loop so the new
* sigq is not orphaned. Nested signal handling is not supported, so
* skip this if we are already delivering.
*/
if (!sq_empty(&rtcb->sigpendactionq) &&
(rtcb->flags & TCB_FLAG_SIGNAL_ACTION) == 0)
{
#ifdef CONFIG_SMP
leave_critical_section(up_irq_save());
#endif
goto retry;
}
/* Modify the saved return state with the actual saved values in the
* TCB. This depends on the fact that nested signal handling is
* not supported. Therefore, these values will persist throughout the
@@ -146,19 +174,9 @@ void x86_64_sigdeliver(void)
rtcb->sigdeliver = NULL; /* Allows next handler to be scheduled */
#ifdef CONFIG_SMP
/* Restore the saved 'irqcount' and recover the critical section
* spinlocks.
*
* REVISIT: irqcount should be one from the above call to
* enter_critical_section(). Could the saved_irqcount be zero? That
* would be a problem.
*/
/* We need to keep the IRQ lock until task switching */
DEBUGASSERT(rtcb->irqcount == 1);
while (rtcb->irqcount < saved_irqcount)
{
enter_critical_section();
}
leave_critical_section(up_irq_save());
#endif
/* Then restore the correct state for this thread of execution. */